HI,
Your poor cat. It must itch a lot if she is scratching till it bleeds.
It is most likely to be allergies and food is the most common cause. Sometimes animals and people can develop an allergy over time or suddenly for lots of reasons. Its possible that the formula of the food may have changed. It could also be eczma.
There are some threads on here in nutrition about allergies and how to best work out what is the source.
Did the vet give you anything to clean and releieve the soreness for her cuts.
Although Kik doesn't have allergies, she does have ear issues and so will sometimes scratch or make her ear get red patches. I use a wash to clean the area and some cream to help it clear up quickly ( can't think of the names right now). She doesn't fight me when we do this so it must give her some relief. Hope others who have cats with real allergies can give you better advice

 

Sounds like MowMow when he eats one of his allergy foods. Cats can absolutely develop allergies after years of eating the same thing.

I put MowMow n a limited ingredient diet(I used Natural Balance venison since it was a novel protein for him) for a few months. Once he stopped itching I started to add back proteins one with a few months between each to see which caused the problems. Then I had a list of what he could and couldn't eat.

For him it's wheat, corn, soy, chicken, turkey, and duck.

Now he enjoys a canned only grain free diet of beef, venison, pork, buffalo, and some bushmeat if I can coax him to eat it. He also gets a raw weekly quail and some no salt added sardines packed in spring water once a week. Oh, and the occasional egg yolk added to his food.

 

Sounds like allergies to me too. Switch over to grain free to start and see if that does not help.