Is she scratching or biting at herself?
Part her hair and look for active fleas. (belly, rump, back and around hind legs)
Use a flea comb and if you are able to comb out 'dander' and 'stuff' place it on a damp, white paper towel. If some of the 'stuff' makes a red ring on the damp towel, it indicates that is flea-dirt (digested cat blood) and that your cat has fleas.