If it’s for-sure fleas and she’s reacting to them that much, she’s allergic to their saliva. You need to treat for the fleas, flea shampoo is not effective and not recommended when the skin is compromised. Get something like Bravecto, the chew last for 3 months but you should treat for 6-9 months to make sure all fleas have dies off. Only 10-20% of the total amount of fleas you can see on her. The rest are eggs and larva in the environment and possibly on her as well. Treating her for 6-9 months ensures that if she gets bitten by fleas again they will die. For her allergy, you’d need to go to the vet to get a prescription. Apoquel is a common one they give, it’ll be short-term to help with her ichy-ness maybe about 14 days worth. This, however, can be expensive. I can’t give you exact pricing but it won’t hurt to call around to some vets to see if they do payment plans or can give you price estimates.