John,
Just read through all of your posts. We have something in common, difficult parents of the person we love. It is sad that some parents are so judgemental and oppressive. Here are some things that might help:
-Understand most young, beautiful girls are the "perfect angel" of the family and the family is overly protective and feels like no one is good enough for them. In fact, they are "jealous" of that person usually. You battle all of this from the get-go.
-It is HER responsibility to tell her family that she loves you and if they love her, they will be supportive. If they won't be, then they don't really love her. Sounds like she isn't brave enough to tell them this and if not, you will ALWAYS have issues.
-I am not sure why they don't like you, maybe that is omitted for a reason, but nonetheless, if you love this girl and want to prove something to her family, then put yourself in their shoes and try to figure what would impress them. Start there and work your way up.
-Tell her that if she loves you to stand up for you and if she won't then she doesn't really love you. You are not asking her to choose you over her family, but her family's cynicism has placed you both in this position. You have no choice. She will always be single at this rate!! You must tell her that it is over if she won't stand up for you and mean it!! You deserve better. I don't even know you and I can tell that.
-It is funny in life sometimes. When we are faced with a choice like this, our real feelings surface. If we are not forced to choose, we never will. We will do anything to avoid the pain. As humans, we are the best at procrastination.
Sounds like you are in a tough spot, but stay positive. You are very young, as is she and 5-10 years from now you will laugh about this, I promise. I'll say a prayer for you, bro.