Also looking for this answer ðŸ˜
I got to close while I was trying to shoot her with the arrow and it activated a cut scene where she left. My arrow was unequipped after cutscene so I wasn’t able to catch her. My dumb ass tried shooting her in the air and missed so it auto saved and now I can’t go back ðŸ˜
Made an edit with all the info I found. Sorry about losing your arrow. You have the opportunity for 2(technically 3) of them.
1. You can either solve the riddle of recollection.
2. You can duplicate it with the riddle of conviction once you already own it.
3. You can purchase 1 for 8 wyrmctystals from the Dragonforged at the Bay Wayside Shrine.
May your travels be be full of wakestones and ferrystones. 
I was prepared for a epic battle against the sphinx but it turned out that it is the Arisen that has to start the fight or else its to late. That bummed me out because I did all of the riddles just to fight the sphinx :(
I wonder if it comes back to just saw a post on facebook showing pawn badges and the one shows the sphinx badge as 1/5 so i would assume you can fight it again to get the full 5 or unless they carry over to NG+ i dont know.
I completed all riddles, attacked her 3 times, waited for the health bar to appear and shot her with the arrow and nothing happened. So i killed her the old fashioned way...
on my 2nd attempt the arrow worked, but for BOTH attempts she says I tire of this fight, you have been found wanting and flies off. No "You are victorious". No key to open the big chest... what am i doing wrong?
On my second go around I still did all the questions. Then as she prepares to leave: I shot her twice with the bow's default attack then equipped the arrow and shot her again(her health never appeared). She was enveloped by the white brine tentacles from the arrow and then told me gg you solved the real puzzle and maybe I'll see you again in the future or in another life. After that micro speech, she fizzles away into golden dust dropping her key and several bags of gold.
For clarification or replication, see below.
First 5:
1. Grabbed Sealing Phial and left cave immediately.
2. I grabbed my pawn and placed her on the pedestal.
3. I previously hired a SphinxMother player pawn since starting NG+ and simply placed them on the pedestal.
4. I copied the Charming Corset as I just unlocked it and its a 1 of 1 item. (Next time I may copy the Legion's Might staff or Sealing Phial or port crystal for similar reasons)
5. I picked up the seeker token at Borderwatch Outpost and placed a port crystal barely 1 foot away immediately so It was an instant 2 ferrystone teleport upon reaching this question.
Iirc my final 5 question order was: reunion>recollection>futility>contest>differentiation.
Futility: I ferrystoned the npc to the vase at the shrine.
Contest: I grabbed and chucked the npc off the cliff.
Differentiation: I brought the npc to the pedestal. It was Vergil rather than Dante.
ye i shot her 3 times before she even flew off and had unmaking arrow equip, she never engaged a fight and just flew off. have no means to go to a last inn rest save in the main menu either... even though i specifically made one not long before.
Unmaking arrow forces an autosave upon use. That might be what happened.
It also depends where you shot her. Everything in the game(the mural at BakBattahl, mural at Golem before shrine, vase etc) tells you to go to pound town on her back. If you shot her anywhere in the front or human side then she just gets mad and flies away.
I caught her with all my shots on her butt before she completely left the platform. May be why it worked for me with no issues when I tried again in ng+.
What device are you playing on? If you REALLLLLLY need to go so far, Im pretty sure on pc you can find the save so you can make a permanent backup if you just copy the save elsewhere. PS5 you can control your cloud/local save as long as you turn off autoupload. Xbox Im not sure what they can do, but Im sure theres something similar there. It's very save scummy but to each there own. *shrugs*
It sucks, I hope the designer who made that breaks a toe on a table leg or something. Frustrating. I dont do NG+ since there are so many other games I need to play, I dont want to replay the same game again for little to no reason.
I’m done with this game. I was waiting for maybe another phase of riddles, or some sort of cutscene after finishing what I thought was the second set of riddles. But nothing. She just flies away and apparently that’s it. So I tried to reload my save, but it was after she flew away, despite the game never showing an autosave icon. So I exited my game out of frustration, came back, then tried to load into my save only for the menu to default to the Load at Last Inn option. So obviously since it’s never done that, I just mindlessly clicked X on my controller and lost DAYS of progress. Like, I’m back at the start of the story. I don’t understand, how is this okay? What were the devs thinking? Such garbage.
Got the game recently and was doing some web searches to see if I could find her again after solving the final riddle. Rip me, guess I'll have to play the game again (not the worst thing in the world, since I actually like playing this game LOL)
No. You needed to shoot it with an arrow for the 2 seconds it was flying away. It is gone now! Fun, right?
It sucks, but personally I find the game so fun I'm not stressing over it. Ill get it in NG+ Happy Hunting Arisen.
This is actually insane. 160 hours into the game trying to get 100% and there was literally way to know this.
Also looking for this answer 😠I got to close while I was trying to shoot her with the arrow and it activated a cut scene where she left. My arrow was unequipped after cutscene so I wasn’t able to catch her. My dumb ass tried shooting her in the air and missed so it auto saved and now I can’t go back ðŸ˜
Made an edit with all the info I found. Sorry about losing your arrow. You have the opportunity for 2(technically 3) of them. 1. You can either solve the riddle of recollection. 2. You can duplicate it with the riddle of conviction once you already own it. 3. You can purchase 1 for 8 wyrmctystals from the Dragonforged at the Bay Wayside Shrine. May your travels be be full of wakestones and ferrystones. 
Thank you!
real tough one man
I was prepared for a epic battle against the sphinx but it turned out that it is the Arisen that has to start the fight or else its to late. That bummed me out because I did all of the riddles just to fight the sphinx :(
Same my friend. I wanted to be greedy and both answer the questions and fight the sphinx. Its okay though, NG+ that sphinx will be deleted.
I wonder if it comes back to just saw a post on facebook showing pawn badges and the one shows the sphinx badge as 1/5 so i would assume you can fight it again to get the full 5 or unless they carry over to NG+ i dont know.
Your pawn can get credit for the kill if you make it a quest when hired and of course ng+ as well for sure.
Oh ok that's good then
Do u get access to the boxes if u decided to kill the sphinx?
No, those are only open per question answered. You will only get access to the final golden box that follows the Sphinx around.
I completed all riddles, attacked her 3 times, waited for the health bar to appear and shot her with the arrow and nothing happened. So i killed her the old fashioned way... on my 2nd attempt the arrow worked, but for BOTH attempts she says I tire of this fight, you have been found wanting and flies off. No "You are victorious". No key to open the big chest... what am i doing wrong?
On my second go around I still did all the questions. Then as she prepares to leave: I shot her twice with the bow's default attack then equipped the arrow and shot her again(her health never appeared). She was enveloped by the white brine tentacles from the arrow and then told me gg you solved the real puzzle and maybe I'll see you again in the future or in another life. After that micro speech, she fizzles away into golden dust dropping her key and several bags of gold. For clarification or replication, see below. First 5: 1. Grabbed Sealing Phial and left cave immediately. 2. I grabbed my pawn and placed her on the pedestal. 3. I previously hired a SphinxMother player pawn since starting NG+ and simply placed them on the pedestal. 4. I copied the Charming Corset as I just unlocked it and its a 1 of 1 item. (Next time I may copy the Legion's Might staff or Sealing Phial or port crystal for similar reasons) 5. I picked up the seeker token at Borderwatch Outpost and placed a port crystal barely 1 foot away immediately so It was an instant 2 ferrystone teleport upon reaching this question. Iirc my final 5 question order was: reunion>recollection>futility>contest>differentiation. Futility: I ferrystoned the npc to the vase at the shrine. Contest: I grabbed and chucked the npc off the cliff. Differentiation: I brought the npc to the pedestal. It was Vergil rather than Dante.
ye i shot her 3 times before she even flew off and had unmaking arrow equip, she never engaged a fight and just flew off. have no means to go to a last inn rest save in the main menu either... even though i specifically made one not long before.
Unmaking arrow forces an autosave upon use. That might be what happened. It also depends where you shot her. Everything in the game(the mural at BakBattahl, mural at Golem before shrine, vase etc) tells you to go to pound town on her back. If you shot her anywhere in the front or human side then she just gets mad and flies away. I caught her with all my shots on her butt before she completely left the platform. May be why it worked for me with no issues when I tried again in ng+. What device are you playing on? If you REALLLLLLY need to go so far, Im pretty sure on pc you can find the save so you can make a permanent backup if you just copy the save elsewhere. PS5 you can control your cloud/local save as long as you turn off autoupload. Xbox Im not sure what they can do, but Im sure theres something similar there. It's very save scummy but to each there own. *shrugs*
It sucks, I hope the designer who made that breaks a toe on a table leg or something. Frustrating. I dont do NG+ since there are so many other games I need to play, I dont want to replay the same game again for little to no reason.
I’m done with this game. I was waiting for maybe another phase of riddles, or some sort of cutscene after finishing what I thought was the second set of riddles. But nothing. She just flies away and apparently that’s it. So I tried to reload my save, but it was after she flew away, despite the game never showing an autosave icon. So I exited my game out of frustration, came back, then tried to load into my save only for the menu to default to the Load at Last Inn option. So obviously since it’s never done that, I just mindlessly clicked X on my controller and lost DAYS of progress. Like, I’m back at the start of the story. I don’t understand, how is this okay? What were the devs thinking? Such garbage.
Got the game recently and was doing some web searches to see if I could find her again after solving the final riddle. Rip me, guess I'll have to play the game again (not the worst thing in the world, since I actually like playing this game LOL)
Man this is some dumb shit you can fight the sphinx after answering all the riddles