QUESTION: My close friend is dating someone who I do not like at all. Should I tell her the really bad things I know about him or is it better to not say anything at all?
CALLIE'S ANSWER: These really bad things you know — are they something that could put your friend in danger? If so, then yes, absolutely say something! If not, I would let your friend find out what she is willing to put up with in the relationship.
Your friend might completely adore what you despise in the new significant other. That being said, keep your mouth shut for now if it is not something dangerous. There is always a thin line in voicing your opinion on someone and you don't want to eat your words.
LILLIE-BETH'S ANSWER: It depends on why you don't like him — if you know some specifics about his past behavior that could affect her directly or information that he is dangerous, then I think you should tell her, taking the risk that she might be mad at the messenger (you). But if it's general dislike, she might not see the same problems than you do and by saying something you could cause more problems between you and your friend. If she's paying attention, she will find out her boyfriend's issues on her own eventually; continue to support your friend and speak the truth when you can, especially if his behavior is hurting her. But I don't think you should let your issues with him cloud your friendship with her.
HELEN'S ANSWER: As hard as it is to remain silent about her boyfriend's shortcomings, hopefully you can figure out some of his good points. Don't share your negative views because if they stay together, she will remember. She will probably get the idea when the three of you are together and the interaction is not so smooth as she would hope for it to be.