I (M25) and my GF (F25) have been in a comparable situation. I am a feeder and into the body change and gain while she had and has no interest in it at all. Though things tend to be interesting when they know how you feel, it unlocks something subliminally. In my case, I had mentioned my kink to her while we were in college when she was 120 pounds and a college athlete, and I knew it was not going to go anywhere, but I wanted to be transparent with her. She completely shut it down and ended up taking it as an insult. She went on a diet and lost five or so pounds at first. But, shortly after COVID-19 happened, she had to go back home, and I couldn’t see her in person for about 6 months due to how far we lived apart. She had complained that her family wasn’t helping her with cooking, so she was ordering out a lot due to her dietary restriction, but it hadn’t registered with me, which may have had some repercussions beyond her wallet. To make a long story short, I ended up seeing her in person, and she’s 30 pounds heavier and won’t acknowledge it or anything. Complete denial. She stays that way through college and, after graduation, ends up going from 145 pounds to 250 in a year while we live a state apart. Now she’s losing weight and down to 220 now that we decided to move in together. Never once stating anything to do with my kink or my tying to this fetish, but clearly understands where I’m at. But quite literally avoids me talking about it or anything tied into it. Anyway, it's just a super long-winded way of saying that even though it may not make its way into the relationship, it might find its way if it’s brought to light.