Sounds quite a bit like an HPD with some BPD elements as well
All those things she is accusing you of (Lying, cheating, contacting ex's ect) are things she is projecting. Further, they are also things she is doing or is on the verge of doing...
Isolating you from your family and friends is right out of any abuser playbook
The prognosis of her getting better is bleak at best. I am sorry as I don't mean to kill your hopeful enthusiasm, but you need to hear the highly probable reality; SHE WILL NOT CHANGE, AND ALSO, YOU WILL END UP HURT. I really wish I was wrong here, but read this board...
You can't help her (only she can) and the more you attempt to or point out her major flaws, the more likely she will bolt abruptly. She has other guys in her radar and it most likely is a matter of time before she will feel you closing in on her true identity. As hard as this is to hear she views you as a source of supply. She has you on a pedestal one day and the next thing you know she will throw you away like yesterdays trash...and that is when they will make plans to leave
You may want to do a search on Panama's posts here. He had a similar situation as yours. Read his story and tell me what you think. In fact, read this board as much as possible. There is a wealth of information
In the meantime, please take good care of yourself. Being with an HPD can suck the life right out of you. Stay connected with your family and friends as they will become even more important than they are now. Being with an HPD... It is like trying to fill a bottomless hole. The highs are great but the lows are crushing. Worst of it all she was acting the whole time
Keep posting to us
You feed the fire that burned us all
When you lied
To feel the pain that spurs you on
~ Alice in Chains