I've only ever found one female feeder and she pushed me hard enough that I managed to gain around 40lbs in just over/under a year (after very very slow gains before that).
Since then though, I've really struggled to find someone I can really connect with who will help take me the rest of the way. Female feeders who are into guys seem very few and far between!
I actually had several who wanted this with me but I declined because I have seen the darkest side of this fetish and the practical application of being superobese day to day so I would rather be extended fat than immobile.