Honestly I'm more surprised that Stheno could control Taylor. If I recall correctly, unlike in the case of Mata Hari where the Male-only qualifier in her Charm is limited to gameplay and is far more powerful in lore, Stheno and Euryale are the same in that lorewise, they are the same in that their Authority is limited to charming males and it was only a quirk of gameplay that turned one into a largely useless Insta-death effect and the other a powerful nuke against male bosses.
So Stheno shouldn't have been able to charm Taylor in the first place.
Huh I'm more familiar with the story she was just some pretty girl who got boned in Athene's temple, so Athene responded the only reasonable way and cursed her.
In Fate, the tale of the sisters is pretty different. Basically, the three of them were goddesses, minor goddesses of the Shapeless Isle. Stheno and Euryale were the "idols of eternal beauty", but unlike them, Medusa was different in that there was something about her that let her mature instead of staying childlike, gaining strength and physical might while Stheno and Euryale remained as weak but pretty as ever.
The problem was? Stheno and Euryale were considered so beautiful that sailors and warriors would frequently arrive in the Isle and attempt to abduct them. Acting in their defense, Medusa took down these "heroes", turning them to stone. But over time, the frequency of the invaders and the sisters tendency to drink blood led to Medusa getting more and more corrupted by the people she fought off.
In the beginning, she just petrified the men. Then, she fought them with her brute strength. Then, the injuries she inflicted became less practical and more for getting enjoyment in the act. Then she started eating the invaders, drinking in their blood. More and more, this continued while Stheno and Euryale watched in horror as Medusa slowly began to transform into Gorgon.
In the end, Stheno and Euryale were forced to make a choice. To try and leave their Isle, leave Medusa behind and fare the outside world, or... meet Medusa for the last time, as Gorgon, before their inevitable end. And though Stheno and Euryale were bullies to their younger sister Medusa, in the core of their hearts, they still loved her. They couldn't bear to abandon her.
And so, holding each other's hands, they walked towards the coiled serpent that their sister had become, surrounded by corpses, and met their grisly fate as one of Gorgon's last meals.