I've given mine some malt that is also peanut butter flavored.

Mine are on a grain free diet and Jane still has hairballs, but I don't brush mine. Such a bad owner, I am.

Not to be negative, as long as you are rural and the mice haven't encountered rat poison, they are good for the diet. I don't let mine eat the mice that make it in the house. Don't know if they have been poisoned.

Good luck with her hairballs.