My sister came to visit me from the U.S. for a few months and she brought her two cats, one is 7 and the other is a year old. My 4 month old kitten gets along really well with the younger cat. She basically grew up with my sisters cats. The younger cat will sometimes groom her and they play a lot and snuggle with each other. Unfortunately, my sister is returning next week to the U.S. along with her cats. How can I help my kitten adjust after her friends are gone?