I'm a fellow FA, and my girlfriend is right on the edge of normal and plus-sized. We've been together a few years and I'm getting pretty sure that she's the one, but she really resents the fact that I'm an FA. It's an issue you touched on in a previous response: the "Am I fat enough?" issue. I find all kinds of fat chicks from a little chubby to really huge attractive, but she assumes that bigger is always better since I'm an FA. Now granted I do have weightgain fantasies regarding her but that's just my lower brain's idea of "best possible thing that could happen without concern for real life consequences." We've had a frank and honest discussion about the issue but I think she's still really uneasy about it, and despite everything probably (still) thinks I'll leave her the minute I find a gigantic woman or something. Any advice?
If she resents you being an FA, she probably resents being on the cusp of plus-sized even more. I've been in your shoes and from my experience, the bigger girls who long ago accepted being fat have had less qualms about staying that way (and weightgain fantasies in particular) than the on-the-fence girls who just know they'll be just purrrfect once they skirt those meddlesome 20, 30 lbs. You can either give her trust issues time to dissolve and see if she's still neurotic years from now, or throw up your hands sooner.
Note to girlfriend about said weightgain fantasies: when someone chooses to date you, it's assumed he or she likes you at that weight. Weightgain is not a "fulfillable" fetish, you don't reach XX pounds and boyfriend is cured of his kink, so girlfriend needs to accept that 1) she'll be doing her share of fantasy work and 2) you don't actually need her to change.
Normally I'd say that she also needs to accept that you identify as a Fat Admirer. But being mid-sized is a tough spot; if you were to bring her to BBW events she'd feel out of place and paranoid, and she could be understandably poky about even being referred to as "fat" if she's not actually. Don't routinely rub in something she could see as a deficiency on her part. If you're choosing to date her rather than a full-blown fatty, take a break from full-blown Fat Admiration.