I'm not going to stand up for my girlfriend
Why won't you, what happened?
When she was younger she destroyed her life.
I'm sure she's expecting you to stand up for her with whatever situation she is dealing with. It's important that you show your girlfriend support by having her back. Otherwise, she'll think you don't care about her.
I'm going to break up with her later.
If you are in a relationship you should have her back. Someone's past does not determine their future you should really give her a chance.