Friend's Girlfriend Using Him?

[Josh]

I have a friend who recently got into a relationship with this particular girl. Memory serves she has jumped around with different guys before. (meaning she hops from guy to guy) This same girl messaged me on Facebook about a year or so back. I did not think she was very attractive or pretty at all, so I just wanted to be nice. I talked to her as if I was talking to any of my other friends. Apparently she took it the wrong way and thought I was being flirty. So she started coming on to me and asking to do stuff with me. Needless to say I said no. She didn't like that answer of course. She accused me of leading her on. Apparently she has a lot of friends because my name at her school isn't necessarily in the best light. When I heard my friend just started dating her, I immediately remembered my experience. I was trying to be nice and congratulate him. However, he later heard her side of the story about me. He has started acting really weird, not talking to me or anything. So a few days ago at lunch, I found that some other people have had some very similar experiences with her. This girl wants to get past second base without even meeting in person. I attempted to warn my friend about this, and he promptly became very angry with me. We haven't talked since. Many other people share my opinion including one of my closer friends from this group of people we all hang out with. We are on a mission to try and save him from getting hurt later down the road. I've known this guy for a little over two years now and he's a bit on the sensitive side and it would just be a rough month for him if she did anything.

So my question for you today is, How can we help him? I feel guilty telling him this, but at the same time, I'd feel even worse if she dumped him for another guy.

Some side notes:
*Neither of us feel any attraction to this girl.
*While I was talking with this girl, she kept talking about a past boyfriend and how it was such a big mistake. (If that clues any repetitive before coming)

[BIG DADDY COOL]

You can tell him, but he may resent you for it. He needs to see it for himself