General

Well, what's she like? What's the relationship like? There's general advice I can give, but there's no one size fits all.

Well, that's nice, but I meant her personality. It's good that she isn't worried about her weight. But is she indifferent to her size? Is she happy with how she looks? Would she be open to gaining?

That's nice to hear. Do you guys have a relationship where you can talk about anything and everything? Is she open to trying new things? Are you open to it as well? Would you be open to trying her kinks as well as yours?

If you already talk about the kinds of things that turn each other on--be it sexy celebrities, NSFW Twitter accounts, or each others' kinks besides feederism--then all that's left really is to talk about feederism itself.

The way I approached it with my new partner was to let them know I had a kink I was embarrassed and anxious to talk about. I also told them that I didn't expect them to indulge my kink at all, and that there were already so many other reasons I was into them that it wouldn't matter if they couldn't participate in it.

It seems you feel similarly, so I'd suggest communicating those feelings to her as you have to us.

Remember that as weird as you think you are, it's possible your girlfriend thinks she's weird in her own ways too. And if any of the weirdness you each have is already out in the open and you both accept or even cherish each other for it, then one more kink isn't going to ruin your dynamic, especially if you're respectful and earnest about it.

Good luck!