It does not sound like a healthy relationship....   You are a link in this romantic chain as much as she is....  Don't spend time determining what's wrong with her...   It's what going on with you....  You get something out of this and that's the pay-off...  You are willing to sacrifice your peace of mind for some reason...  "the pay-off"..  

Your home work....
What do you want out of this relationship that's worth this trouble...?

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