My cat had skin cancer. This was frozen off. The vet believes it is gone but the wound will not heal

Question

She cannot smell so will not eat.

Answer 1

Take her back to the vet or call them immediately. make sure the wound doesn't get dirty, and keep her away from other cats until you get to the vet.

Answer 2

How long has it been?

It should have scabbed over and healed within 2 weeks.

If not, there's something else going on.  Have blood work done to be sure there are no underlying issues.  Lots of times the cancer you can see is "the tip of the iceburg" and there's plenty more you can't see.  Blood work will catch that.

As for feeding:

See if you can find a canned cat food called "Tiki".  It's the most stinky stuff I've ever found.  Cheap cat food tends to smell the worst.  Try Fancy Feast or 9 Lives.  Warm it up in the microwave.  Warm food smells more.

If you're feeling generous, canned sardines stink pretty badly.

If she still won't eat, go to the baby aisle of the grocery store and get Pedialyte water, a medicine shooter (the syringe is easiest, but the eye dropper type will work) and meat baby food.

Use the Pedialyte to water down the baby food (which is more pure and nutritious than most cat foods) to a thin paste.  

Use the medicine shooter to drip the food in her mouth.  DRIP!  Don't choke her.  If she licks it, great.  If not keep dripping as much as she'll let you get into her.

EDIT TO ADD:

Giving an adult cat kitten formula may upset their tummies.  It doesn't provide enough nutrition for them either.  Go with meat baby food, canned cat food, or there are nutritional pastes that some cats will take.  Try Nutrical.  It's available at most pet stores.