She likes him but he's a pervert - what advice do I give her

I would suggest that you just be honest and forthright about what you've heard. Make it clear to her that they're just stories and might not be totally true and might not entirely reflect the guy's character. Don't make it so she feels like you are pressuring her to break up with him; just be the info sharer and let her make up her own mind. Be her friend regardless of what she decides. Sometimes people don't act on friendly advice immediately, but she may take a more skeptical look at this guy and not tolerate any bad behavior if he shows signs of living up to his reputation. That could save her a lot of grief later on.

If she has not heard anything about this person why dont you tell her what you know and where you have heard it.Also explain to her that it is her you are thinking about as you would not like to see her hurt and if anyone else knows what he is like tell them to tell her.Happy Mylotting.

Be honest with her about what you have heard but say it in a nice way.

do you think these stories are definitely true or just gossip? maybe you can tell her to be careful, don't know what else you can do apart from be there if he does turn out to be an unfaithful git.