I think it's very sad for the cats that their lives have changed so much since B. left. Bootsy, B's cat, appears to have adjusted, while Lucy, my cat, is having a harder time. (B. gave her a lot of attention while I was at work.)
Or maybe it's the "thing" (to quote the vet) in Lucy's abdomen, which the vet had originally thought was an enlarged kidney. A subsequent blood test determined that Lucy's kidney function was normal. Now the vet doesn't know what "the thing" is.
Tonight I bought two boxes of Fancy Feast cat food. Maybe that will help. Both cats no longer eat much of the dry food they've been fed for years, which was always supplemented by a can of wet food.