If she's taken a rat before, the hardest part is over, you just need to stay consistent with only offering rats. Are you feeding live or f/t? If f/t, defrost the rat with a mouse together in the same water. Then when ready to feed, rub them together focusing on the head, make sure to get a good amount of the mouse sent on the rat head by rubbing face to face. If feeding live, put the rat in a bag of used mouse bedding, the dirtier the better. Shake the rat around in there with the bedding a good amount and that should get enough mouse scent on the rat. This should work almost every time but if it doesn't, do not feed the mouse. Wait a week and try the same thing again. You'll probably need to get her to take 3-4 like this and then start trying the rat without the scent of the mouse. Once she has taken a few unscented rats it should never be an issue again unless you give her a mouse again. Don't ever go back to mice or you may need to start over, some of them really prefer mice so once they get a mouse again, they will sometimes try to hold out for a mouse. Good luck.