two strays one gone?

My mom has been feeding two strays at her apt. I have pictures from 2004 so they must be about 9 or 10. They survived the harsh winter by staying under the deck. These two cats were best friends and would cuddle together in the sun on the deck. About a month ago the female cat looked thin and tired . She ate then lied down on the deck then got up and lied down in her cat carrier. I have had cats all my life and I know something was up. Well I have not seen her in a month. I feel so bad. My mom has dementia and does not know the difference and still says her cat outside stands and smiles at her without(her) realizing the other is gone. I know They have worms did see it in spit up once. Anyhow what causes them to go off and die old age or can worms deplete them totally or disease. She( the one that I do not see) did have darkness in the corner of her eye. She still feeds the one male who looks so lonely but he has my mom! he loves her.

I am sorry for the missing cat. This does happen frequently with the feral cats, unfortunately. If they become sick/old, they will go off and hide somewhere and will pass on to the bridge . I lost a dear feral a couple of months ago. It is a tough reality that we have to deal with. We never will know for sure what went wrong with them. They just never come back. I am sorry for the male cat that he lost his companion. at least this cat has your mom to care for him. Sounds like they do love eachother