I tend to say exactly what I think, so if you might be offended don't read anymore of my post.
If this girl is so easily manipulated by her mother, she has a REAL problem. I was married to someone once, LONG ago, that was truly a manipulative socio path. She didn't get it from someplace strange. Her mother was off too. Not to the degree of her, but still had problems.
If you stay with this girl, in all likelihood, she will be as bad or worse than her own mother. You want to marry a version of her momma that is the same or worse? There is a reason for that old "look at their mother if you want to see what she's like in 10 years". Because that is pretty true.
Magnify that by a decade of marriage and then you begin to involve children in the mix. Want to curse your future children with her mother's issues? It's a vicious cycle that only YOU can control. As an adult she apparently can't see how bad this is, or she would escape it. She is dooming herself. You want to be chained to that too?
Do some soul searching. At your age, it SEEMS like this is the most important thing in the world. It's not though.
Do yourself a favor, and take a year away from all the crap. Meet new people. Enjoy the company of other people. Put this behind you. If not, I can tell you this just will not end well. It never does.
Good luck.