Well, it is good news that your husband is supportive of your relationship with your girlfriend, and that you have worked things out with him. Sorry to hear about the mess with your girlfriend's ex. The best you can do there, I think, is offer moral support.
"She definitely hasn't had a healthy relationship, and tends to let people treat her badly. The caretaker in me wants to fix it, but I know I can't and that is really hard. I also worry she's not getting what she needs, but won't voice that concern because she hasn't had that freedom before."
I think it is a good idea to allow her some freedom, even if it means letting her make some mistakes. The lessons she learns on her own will be the lessons that stick the best. Just let her know that you're there for her.