Mine also do that "looking interested but jk nope" thing when they are off feed/fasting. It's normal.
You'll only need to worry if she loses significant weight, becoming really skinny- then there might be an underlying issue.
She will lose a bit of weight over the fast though, that's normal. Most likely you won't have to worry. They always get back to eating eventually, whether it takes 2 or 5 months. Just offer once every other week, and don't over-offer.
How much does she weigh now?