Well the other companions don't exactly tell you that you have been treating them like a lover when you haven't or how they'd like to screw you and whomever you're in a relationship with at the time (no, "thinking like animal" isn't and never will be a good excuse). The only one that comes close is Astarion because he's obviously trying to use and get close to you when you first meet him in Act 1, pretty evil at this point in time. Or maybe Minthara when you reject her, who's also supposed to be evil. Halsin just acts like a creepy teacher who's trying every trick in the Fboy Rulebook in Act 3, that's all.