Cat Has Itchy Neck?

I just moved to a new apartment a few months ago so it could easily be allergies. My cat is scratching her neck, I haven't looked closely at it, but it feels like the little scabs she had all over her skin when she had fleas. I am a poor college kid so I'm trying to figure out what it is without taking her to the vet, but I feel like it's about time to go to the vet anyway. When she did have the scabs all over her body I decided it was flea bite sensitivity, I treated her for fleas. Everything went away, but around her neck. She is still eating fine and acting like herself, but she is scratching her neck like crazy. I don't know if I should worry about her or just wait and see if it just goes away since she's acting fine.