I am not a vet but it sounds to me like your cat is ingesting the spay probably by licking its fur. I had a similar problem with my cat and had to generalize the area I was putting the spray on (my cat had ringworm so I only had to put the spray on the spot). I used a q-tip, dipped it in the spray bottle and applied it this way. Not sure if you are able to spot use the spray, you may want to try to give her a flea bath, if you cannot handle the cat yourself in the bath, which most do not like, take her to a vet and have them do for you.
