"More so than I would have expected, frankly." They've hit on something governed by a bit of Law, maybe? Or a pattern, a 'trope'? "Is it - something you would find acceptable, if it was something that Carissa found acceptable? Maybe I should back up and ask whether Carissa has even said anything to you yet about you getting to decide who she sleeps with? Because if she hasn't, I would predict that you wouldn't need to ask her explicitly, just wait for her to raise the topic herself."
(There is an art form to these things, you don't ask someone, 'Do you find that unacceptable', because then they'll look for reasons to reject it, you don't even ask them 'is that acceptable' and wait for them to consider the contrary, you add on clauses like 'if Carissa found it acceptable' so they can focus on that and then add another topic afterwards. You don't want them to have nothing to think about except the question of what unacceptable aspects they can find.)