Breaking up is really, really, TRULY!! hard to do.
But you gotta do it, if the love isn't there any longer.

You two had a plan you'd agreed on, you followed it--tried to--she didn't.
Now you need to follow through with it without looking back. Do it.

Do it.

Be a grownup, live your own life for yourself. If her family isn't supportive enough to help her through this time, she needs a good counselor. That isn't your place now. This isn't a LifeTime Movie, so please don't try to be her friend.