I agree that she might do well with a buddy, and I also agree that a younger cat would probably bend to fit the household more easily than an older cat already set in her ways. I don't think it has to be a little kitten. A "catten" (adolescent/"teenager" ) would be okay too, and they're often hard for shelters to place. Schmoo can boss a younger one around and teach it the rules of the house; an older cat might be too established in its personality to fit in easily.
Some cats do just fine as only children (my cat is one of them); others really need a feline friend. It sounds like Schmoo may be one of them.