My name is KitKat!

KitKat was found during a snowstorm at the Colorado
Springs jet center in October. She was in excellent condition. She does have a clipped year suggesting she was caught in a trap at some point, but none of her behaviors are consistent with ever being an outside/feral cat. Her picture was posted in the area and she was listed as a lost cat with several agencies. She does have a tipped year and has been spayed. Nothing else is known about her past. She is extremely affectionate and loves to play with toys. She has made no attempt to go outside since at our home. She is litter box trained and has not scratched any furniture. She has kept the dogs at bay by hissing even though they are friendly to cats.
The problem lies with our older cat who has not adjusted to KitKat and is showing increasing signs of stress. KitKat has polydactyly, 6 toes on every paw. She is very loved, but we have a rule that we can only bring another pet into our home if it has no negative effects on our other pets.