It depends on the color of the beater. Some KitchenAids have the coated finish and some have the "burnished" finish. This sounds like the burnished finish, which I have read other people having the finish come off. She'll probably have to buy a new one, available on their website (
http://www.shopkitchenaid.com/webapp...rm=flat+beater) or ebay.
I have washed my coated one in the dishwasher, no problem. I use Finish.