First off, you shouldn't have gotten involved with your friend romantically if you had no intention of perusing a relationship with her. That is just plain wrong and sets you both up for pain. I mean, one could call you a tease or player or something. Don't get me wrong. I'm not saying you are those things, it's just that you went about things all wrong from the beginning.

She IS manipulating you though, so best distance yourself from her and call 911 when you feel things warrant it.