@LastNight she's probably either observant enough to know MC had been checking her out, or she figures with THAT body whatever he's into she's got it.
And yeah he'd jump her if she weren't as high up on the crazy axis as she is on the hot axis.
I'm pretty sure at some point she'll unleash her huge boobs for him as thanks lol. And he won't understand why she's doing it. That's how these stories go.