99.999% sure that it is fleas, she needs a flea medicine FROM THE VET not the store and she should be fine. She could have allergies from it too, if the scabs are really bad, my one cat is allergic too.
I see so many cats like this and a lot of times the owners don't know what it is. I was in a little local pet store and they have a few cats that roam the store and one is just covered in scabs, some to the point of hairloss in several places. I asked the guy what is wrong with the cats and he was like "oh i don't know, it isn't a disease or anything" I am thinking about anonymously sending them a letter about it and suggesting what they can do for the cat. I don't know, I don't want to get in trouble or sound threatening or anything.