Rash?

I just noticed this today (as I don't remember it being there yesterday) but it looks my cat has a rash on one of her legs? My mom said she might have laid in something sticky but it looks like some of her hair is gone too.

I'm really worried about this and I am not sure what to do... She won't sit still to let me get a decent picture...

I'd get her to a vet. Looks a bit like ringworm.