Nicky may still be grieving, and it may take a while to get over losing her friend. A 9-year old cat may or may not play with a kitten. Did Nicky used to play with Lindsey? I've had some older cats who were content to just sit/lay and watch the kitten antics. The suggestion that you get another kitten for your kitten may be right on target. If you don't, as the kitten you have gets older (in a year or two) and settles down some, s/he may become buddies with Nicky. Right now, compare it to a 60 year old person having a toddler as a friend. I don't know what 9 years old is in comparison to human years, but it's up there.