Johnny & Cassie BR
It seemed unnecessarily mean to tell the girl that Nick had never actually mentioned her to him. Johnny was definitely smart enough to surmise that they had a tense sort of relationship or whatever. Bad enough that she didn't like his super handsome face over it.
So instead he just gave her a look that said he didn't quite believe her. "So things are screwed and you're here dancing with me hoping he feels bad about it?" That made sense to him. He totally got how the minds of teenage girls worked. "Okay. Got it. Just going to say it might be more effective if you actually looked like you're having a good time. Or at least like you don't hate me."