How do you warn your friend?

When I'm in situations like those I'm pretty forward about how I feel. I wouldn't be rude about it and say "That person's a douche," rather I'd say "I don't have anything against this person, but I'd rather not mix with him or her. It's just a gut feeling."

Thanks for the reply! I would do that except my friend's the type of person who needs proof/"examples" of what has happened. Actually even then she doesn't usually believe them until she sees things herself. If I were to say it's a gut feeling it will be brushed off lol. Another problem is that guy A has a tendency to twist facts. If you were to catch him in an outright lie he would pretend he never said it at all. Which gives me a major headache because even if I were to say what has happened I can't guarantee he won't try to turn things around. 😕

Some people are like that and have to fall before they believe the people warning them. Just be there to pick B up if needed. If you've told her how you feel and it isn't good enough, then that's on B and not on you. Frustrating, but that's life. You can't go wrong with honesty.

I agree with above. Be honest with your friend about your decision to stay away. Don't tell B what she should decide, just make sure she knows what you decided. And be aware that anything you say could very likely be passed to A. So if this matters, be careful with your wording.

Thank you for your advice! Will try :)