Your cat will remember you the rest of her life (subject to dementia). That’s the short answer. Cats have good long-term memories in my opinion especially with respect to their human companion/guardian.
I have to rely on personal experience to answer this question because the reference books that I have don’t really answer it properly.
My mother’s ginger tabby
My mother loved cats. One of her cats, a ginger tabby, decided that he wanted to live in the wild. He went across the road and lived on the golf course opposite for very many years. It must’ve been 10 years, perhaps more.
One day he came back riddled with arthritis (walking sideways) and looking very old and tired. He decided to come home for the warmth and to be fed. Of course he remembered where his home was and he remembered my mother as if it was yesterday. He was wild and difficult to handle but he was home. I think that this is a good example of a domestic cat’s long term memory.
Another ginger tabby
It is interesting to see that on the Quora.com website Bridget Swain recounts the reunion of a ginger tabby cat that they had looked after. One day he disappeared and they thought he had been stolen or simply wandered off. At least four years later they were sitting on the lawn and spotted a scrawny ginger tomcat across the road. Bridget’s mother shouted out that she had seen her cat. The cat dived into some bushes and her mother followed. She emerged with her cat in her arms. Her cat was ecstatic, wrapped around her shoulders and licking her hands.
She took her cat into her home and he settled down as if nothing had happened. He went to the same place he always slept and asked her for food. He picked up where he’d left off at least four years earlier.
Cats need long term memory to function
There will be countless other examples. Cats remember past experiences which may have traumatised them. This affects their behaviour in later life. There is nothing to suggest that domestic cat should have poor memories. Domestic cats love routines and those routines are built upon memories. That’s the only way that you can become accustomed to routines.
Strong memories – better memory
I’m sure, however, that the better the experience a domestic cat has with his human companion/caretaker the stronger his memories will be of that person. If the relationship is rather poor between person and cat, although the cat will remember the person he might not want to associate with her. It seems to me that he may give the impression that he’s forgotten the person.
Wild cat survival
Looking at the issue candidly, I don’t see how a cat could really function properly unless they have a decent long-term memory. The domestic cat’s wild ancestor is the North African Wildcat. They have to use long-term memory to survive.