I can't tell you what to do, but it sounds like you and her see the world very differently. We've all been hurt or "victimized" in some way or another, some more than others. That's the hand we were dealt. But life is made by doing the best you can with what you've been given. Complaining that someone else had it easier accomplishes nothing, except create an excuse to not improve yourself and your own life.
Maybe she's just immature or temporarily depressed. Or maybe she will always view everything in the most negative light, looking for reasons the can't do things and can't be happy. Compare that to someone who always looks to make things better and happier, no matter what the obstacles thrown in front of them.
If you marry her, will you be the target for her blame, as to why she is never happy? Or are her feelings just temporary due to extenuating circumstances?
Answer these questions for yourself.