M.R.
Maybe she does not need a nap? Can you pick her up before naptime? This just sounds like a bad fit for her little personality. Not that a child of 4 1/2 should not be able to meet some expectations that she finds less than appealing, but this one sounds beyond her reach. If the stuffed animal is not helping her, you should find anther motivation, but don't expect that to help her in this situation other than to frustrate her because she cannot earn the reward, it may just be too much to ask.
M.