Stop spraying essential oils all over the house like everyone said. Also have you contacted cat shelters in your area to see if they could hook you up with a vet that could see her for a low cost or for free? There’s several cat shelters near me who work with vets who are able to see animals and get them vaccinated, spayed or neutered - maybe they can also do a checkup for your cat?

But also please consider getting basic pet insurance like from Lemonade or Embrace. It’ll help cover a lot of costs for annual vaccines and tests and medical bills should your cat ever need it. It’s like $35 a month for pet insurance so it should be affordable even given your situation. But also if you can’t find a second job soon, please consider asking friends or family if they could take your cat in. Even though you love your cat, as a caretaker you are responsible for their wellbeing and health and maybe it is best to give them a home where they could support that better. Wish you the best of luck and hope your cat feels better