Wow, you are in a tough situation....I would say any toxic relationship is horrible to be in, jealousy is a very strong emotion and it does tear people apart. The fact that she flirts with other guys when she is dating? That is a MAJOR red flag.

When you had/have some personal issues (I hope your okay :D) she should be there to comfort you, but maybe she was a bit nervous to help? You mentioned she is driving your friends away and honestly that's A DOG MOVE! I guess you feel guilty because you had all these good memories and now you can't share more. The best option if maybe talking to her about how you feel and if she doesn't come around and shrugs you off than, I say move on and find friends that actually care about YOU and your well being!