How old is she?
She may be too young for food allergies but maybe environmental.
I would recommend not using flea collars or Hartz products ever.
Hartz products have killed several animals.
HartzVictims.org - One More Victim is One Too Many
If you have to use something for fleas, how about Frontline or Advantage?
She could be allergic to any of the ingredients/pesticides in any of the things you listed.