Feedmesqueezeme:
Only if your gf has explicitly said yes she is into/open to gaining should you be feeding her and from what you have said she isn't.
You are non consentually making her take part in your kink.
My best friend is a bigger woman, but she is emphatically
not a feedee.
She slimmed down considerably and was loving how she looked and felt. Then she dated a guy that, in hindsight, was at least a chubby chaser. She dumped him for a number of reasons, but one that stuck out was how he was always taking her out to eat and never wanted to go anywhere healthy.
He stayed in shape, but she gained about 30 lbs. They were together for 5 months. Her self-esteem is shot, and she feels gross. I catch her beating herself for not saying no from time to time. She says the reason she went along with it is because the food was good and it made him happy.
This is what happens when you push your fetish onto a non-consenting party. It messes them up and makes them miserable. And if you really loved your girlfriend, you'd never dare do something that would make her miserable.