Kill the hag, get her hair and save Myrina - Epic win

[EvilDonut]

There is a way to do that. All you need to do is having one party member in constant stealth during the fight, then you move that member where the hag spawns and swaps into myrina and keep him stealthed.
When you hit the hag enough, she will start a dialogue, pass the check to save both Myrina and have the hair and as soon as you picked which hair to obtain, quickly switch to the stealthed character, who's outrside the dialogue. Now, with that character, hit the hag, she will not teleport away cause she is still inside the dialogue.

Profit

[Bunny's Princess]

do you need to one shot her?
and does it count like killing her normally

[EvilDonut]

No, you do not need to one shot her because she is still locked in cutscene and cannot move.
And it seems it does count like killing her normally, because the guy who was turned to stone is still alive and de-stoned

[Pigsnortcore DSP style]

I don't give a f*** about that dumb chick. No need to waste a save on her