Fuck, I’m not sure I have anything much to say for advice (except get her some guy she can victimise instead) but your situation sucks, it is NOT your fault, and you have every right to feel pissed off and trapped.
A lot of people have ups and downs in life but you have this situation where she grabbed a hold of you at a bad low-point and you can’t bounce back.
Maybe try calling the Angel of Lost Things, see if you can get your lost freedom (not being silly saying that, it’s as real as anything else)?