You literally just said you were mad.
Kara: I was mad at you because I thought you were dating Eve.
Mon-El: Were, as in past tense. Right? As in, she told you the date didn't actually go well.
Kara: Yeah, she mentioned it.
Mon-El: You know, I'm not super hip on earthly social cues, but why would you be mad if I was dating Eve?
Kara: I'm not mad.
Mon-El: You literally just said you were mad.