She's 31 and is still being manipulated by her family. This will definitely continue after marriage and I promise you, it will cause A LOT of problems. I have seen a lot of marriages fail by letting family meddle and manipulate. Why do you want a marriage like this? I know it can be difficult to find a decent partner but you shouldn't have to sacrifice your dignity in order to be in a relationship.
Why do you keep getting back with her? If I were you I would give her an ultimatum. She's too old to be acting like a child and letting others dictate her life. You don't need someone like that, I'm sorry. You may want to analyze and ask yourself why you keep getting back together with her. I don't know you but it's defintely not healthy to want to marry someone like this woman. You're willing to sacrifice a lot for her and it sounds like she's not doing much for you.
Fyi: I have worked for a divorce attorney for 10 years. I have seen your kind of relationships fail very frequently. If they stay together it's usually because one of them is always putting up with all the crap. Eventually they get fed up and leave or stay and suffer from all kinds of emotional and mental issues.