I also do fasting, but found that standard intermittent fasting did give me some weight loss, but like other things eventually leveled out. Then I added longer fasts once a month and am seeing more progress.
I’m not sure that you’re effectively reading her mind here. One of my initial issues with fasting was I’d heard that it would eliminate my metabolic rate to something entirely unuseful. I’d been told the standard athlete 4–6 small meals a day was the way to go. What it did was crank up my blood sugar every time I ate. I now eat 1–2 times a day and either stay the same or lose. So I had this pre-diabetic state (allegedly) working against me and didn’t know it.
The thing is, if your method sounds like it’s against common wisdom and as if it might hurt you, I can see why someone might be resistant.