I recently lost my 15 year old kitty to lymphoma and he lost his appetite on and off for months until he lost it completely. Although in 2017 he also completely lost his appetite for a while due to an infection and I did not know he was sick until he stopped eating and became lethargic. They said if I had brought him in any later then he wouldn't have made it. Definitely see a vet if you haven't! When a cat stops eating it is usually for a very serious reason like illness, and even if it isnt due to illness if you cant get them to eat it can quickly become serious due to the stress and damage on their livers. If you have and are just looking for advice to encourage her to eat, I would often buy Max different kinds and flavors of cat food. I threw his previous "no grain" diet out the window (he had a skin condition the grain could worsen) and just bought whatever I thought he might eat. Mixing things up helped him to feel less bored of food or would get him a little more interested. During the end of his life if he threw up any food he would not touch that brand/flavor again so I would make a list of what I knew he wouldn't touch and not offer it again due to increasing his aversion to food. The vets also gave him prescription food that helped for a while. But it is really difficult to get a cat to eat if they don't want to. Nearly impossible. A vet could also prescribe an appetite stimulant or put them on a feeding tube until they're able to eat on their own again. Max had to use one before. Also if vet costs are too much you can sometimes work out deals or payment plans by talking to the vet clinic. Cat clinics especially are very helpful. I also used Care Credit to afford Max's bills from 2017 and was able to pay it off for 1.5 years without interest.