I can't say I'm sure how it could've been ended differently, but it really left a bad taste in my mouth.
I found most of the story excellent, and the art is wonderful. However, something really does not sit right with me having someone with PTSD end up with a violent sociopath. As someone who's witnessed these dynamics first-hand, this does not create an environment for healing. It creates an environment for further abuse. I found myself getting more and more annoyed by how characters acted as it came closer to the end. Camilla, Amy's best friend, is somehow won over by BiBi? This person who's been nothing but awful up until that point? No amount of "they went to therapy together!" after the fact is gonna make any of that better for me.
This may have a been a bit ranty but I found myself legitimately bothered by how it ended. Bleh.