Cat Health Question

For many years I have referred to this amazing site for many cat questions but now I have one that maybe someone can help me with.  This is long and I'll try to keep it brief.  One of my cats has been to my vet several times for hair loss, dental issues and hot spots.  I rescued her grandmother, mother and sister who sadly have had put down for dental issues.  After numerous teeth cleanings nothing seemed to work.  My vet said the only solution was having their teeth pulled.  I can't afford a dentist for myself let alone my cats.  After I had her sister put down is when she started licking her hair off so I took her to the vet.  He said it was probably allergies and gave her a depo and convenia shot which I'm not happy about.  I thought maybe it was separation anxiety from losing her sister (they were very close) so I bought some comfort zone diffusers which helped for awhile.  Since then she's been back to the vet several more times for more shots ( which again I'm not happy about). The hot spots were really bad.  The last time I had her in I decided to buy a bag of the Royal Canin allergy dry food thinking I would try the allergy route.  She's hardly eating now.  I'm pretty sure it must be her teeth so I've been giving her some canned cat food just so she eats something.  Does anyone know if dental problems can be genetic?  I've read certain breeds can have problems but all my cats have been rescues.  I'm just at a total loss as to what I should do next. BTW I'm in a dinky town with not much available around.  Any suggestions will be appreciated.  

try just baby food and see how she does..

Thanks!!! I never thought about baby food.  In the past I've given my cats squash baby food for constipation/diarrhea and it's worked.  I'll just make sure the baby food doesn't have any onions or garlic in it and get some tomorrow.