When I adopted Scrappy Two , Miquelito and Pouncierge it was like a charge of energy to My Older Cats , like Moose the Magnfi Cat and I think that a friendly Young Lady Cat would give Boo a New Friend, and give that Poor Cat a second chance.
A nice Mature Lady Cat would give Big Boo a friend to sit with, and add a bit of a spark to the Old Fellow.
Joseph, Michael and Princess love My Kitten Trio and they often play together which I am convinced has added years to My Senior's lives!!!