If you friend's boyfriend was cheating on her and she knew but wouldn't leave him, would you talk to him?

LOL WTF... I'm not sure I'd want to be involved with any of this. I wouldn't get involved in her relationship... it's not like she doesn't know what's going on and you'd be enlightening her to anything. Plus it doesn't sound like your friend is REMOTELY stable so I would handle her at a very safe, guarded distance.