Friend likes a jerk

So last year there as this guy named junior who was talking to one of my really close friends and he wanted to have sex with her for a while but, he only wanted sex and nothing more. My friend was completely in live with him and has been for years so she accepted. They never actually went through with it but they did send each other nudes back and forth for a while but it stop when he went to Europe for a trip. I finally convinced her that all he wanted was sex and he wasn’t going to get into a relations with her.

So then at the beginning of this year my friend’s best friend started to send junior nudes and would tell her about it every time she got them back. So now they aren’t friends anymore and junior was also talking to 4 other girls getting nudes the whole time.

So now my other Christy is talking to him and I told her the situation with him and SHE WONT STOP TALKING TO HIM!! I get that I can’t tell her what to do but I already know she’s going to get hurt and she already knows he’s talking to other girls trying to “see which one he likes best”, and those were his EXACT words.

I know that she can do whatever she wants but she really likes him but obviously he doesn’t like her enough to only talk TO HER. I’ve told her so many times it I just don’t know what to do anymore.

Can anyone give me advice on what to do? Or if i should just leave it alone?