You say you care about her as a friend. That might be a bad idea. Is she really a friend? Friends care about each other. Does she care about you at all? Does she hope the best for you? Does she hope that you find someone that makes you happy? If you're dating someone and tell her about it is she supportive?

Ask yourself: is she actually a friend to you at all?

She does not sound like a friend. She sounds like she's using you to get some kind of perverse enjoyment out of telling you about her sexual exploits and watching you squirm.

The crazy thing is YOU have all the power here. Block her number. Block her on facebook. Block her emails. You don't even owe her an explanation. She'll get along fine without you. She does not need your "friendship" and you certainly don't need whatever it is she's giving you.

Wake up man. She's not good for you, and you are not even doing her any favors by letting her treat another human being this way. All you have to do is simply exert the control you already possess. End the bullshit.