What do you know of her family? Are her parents still married? Is their marriage intact? Does she have siblings who behave the same way?
She sounds very insecure and, perhaps, needs to grow up a bit and focus on something other than herself. She sounds very self-absorbed and there might be an underlying reason that even you are not aware of.
Like I said, at your age, I would be keeping my life playful, happy, and free of negativity, particularly by avoiding the live-in situation with someone. You've got another 80 years (or, more) to live your life. Smile. Relax. And, think about what it is that you're expecting to gain out of your current relationship.