Although we would all like to have our own personal "crystal ball" to see how our decisions will play out, as this isn't a reality we have to base our decisions on what we feel is a likely outcome and err on the side of caution, especially if it will impact on individuals besides ourselves (including our pets).

Not having had the opportunity to develop inter-cat social skills, with a cat being sedentary and set in her ways, and recognizing the exuberance that a young age brings (most of which will be directed at an older cat) suggests that it would be unlikely that the relationship between an older cat and a potential new cat will be a mutually beneficial one. The stress could impact on her health, compounding any current health problems or age-related arthritic changes that she may have, or result in behavioural problems such as hiding and loss of house-training.

Perhaps a visit to your veterinarian for a thorough physical and discussion on how this decision would impact your cat is in order.