A lot of negative feedback. I don't interpret it the same as these other guys do.

Although they may be right.
Here is what I say. This is theoretical knowledge and I have never experienced what you have.
She is upset because she feels awful. She loved a man with all of her heart, and he crushed her heart with his every word. Then he shit on her heart. This man is a very bad person. He is very troubled young man. Now I don't know your relationship with this girl, but you need to be careful how you proceed from here.
She obviously needs love. She needs assurance from you that you love her or at least care about her unconditionally. I don't see her leaving you for him. I see her being horrifed of you treating her the same way he did.
Dude, what is probably happening is what we called a self-fullfilling prophecy. She believes she is not worth anything because of her experience, so her mind is making her do things to prove to herself this is true. We in PUA call it self image. If you really care about this girl then you should boost her ego. If you break up with her after what the other guy did to her, she will be completely fucked for life. Don't do that to her man. Please don't do that I beg you. I actually have a tear in my eye because of how much she is hurting. She needs your love.
Sincerely,
Magnum45