It's not much later, in Isabella's room, that she asks:
"So... is Alex really a dom?"
"I mean, when you're setting the movie up, or between bites like we're doing right now, or before you go to bed, or after you wake up."
"Well, couldn't you? Next time you're having a not-sex time together, you could ask him not to use the whatever-it-was."
"'The thing you used last time' should be enough, unless he used lots of things, in which case you can try to describe it, or point at it when he tries to use it?"
"Okay, but, like, you have to have a reason to think you wouldn't be able to do a thing. And, it's a relationship, so, by default you're assumed to be able to choose what things happen?"
"Um. No. No it's not. As far as I'm aware, and as far as all those sex ed pamphlets and classes say, the sub can also choose what goes on in a relationship, because relationships are supposed to be mutually satisfying," he explains carefully. "That is also the reasoning behind safewords and aftercare."