I think you should try feeding her mice. It has happend to me before, well not the same thing, but I have some balls who prefer mice over rats, or rats over mice and I would thaw them all in the same container, and none of them would touch their food, so I had to thaw the rats in one bin and the mice in the other. Maybe she got the taste of the mouse and preferd it?? not sure, if you havnt already tried a mouse try that. and if it works, just scent the rat from now on and she will get use to rats.
I had bought an adult ball off some guy a year ago and i could not get her to eat, i tried everything, she was seirouly on the verge of dying and this guy would not get back to me. So i tried hamster, and she pounded that thing, so i just scented all her rats with hamster bedding a couple times now she take rats no problem.
Hope this helps.. Good Luck!