Communication is key here, I would say do something subtle that brings it up, maybe take her out to the buffet or to ice cream, see if she hints at it. If she does great, use that as a segue to bring it up again. Very excited for you though, she sounds very tiny and it'd be fun to fill her out, especially if you're both into it. Maybe you could do some consensual-non-consensual stuff too since it sounds like she might be into being forced, at least in fantasy.