Cats are very social animals, and they do miss their companions terribly when they are gone.

Would it be possible to get a friend for her? A neutered male would probably be best, adopt from a no-cage type of shelter so you can see how he interacts with other cats. You'd like one that is social without being dominant.

There will be an adjustment period, but then I'm betting they will bond. Best bets are one that's around her age (a cat like that will really be in need of a home, too) or a pair of younger ones.

I'm very sorry for both of your losses.