Are you using Revolution on her?

A couple of thoughts:
Revolution can cause hairloss in a small percentage of cats at the application site. That spot, from what I can see, is pretty well centered on her back, at about the spot most flea products are applied.

Allergies in cats can manifest as scratching in that particular area. I have a cat who breaks out every year or two and has to wear a cover until it's totally healed, or he claws it raw.

Ringworm most commonly shows up in cats on the face and ears, and typically has the classic red ring, with a pale center. Grey scaly patches on the body are more typical of ringworm in dogs.

All that aside, the clotrimazole won't hurt so there's no harm in prophylacticly applying it now. I've also had terrific success with Resizole leave-in conditioner. Nothing like having half a dozen gloopy wet cats sulking in carriers and glaring at you. :-)