Thanks guys. She does seem to be less energetic, but it has been very gradual and I have just put that down to her age. My daughter is 3, has only started taking notice of the cat, and just wants to cuddle/kiss her constantly, Molly(my cat) has a great nature and seems to put up with it, but I know that she doesn't get a minutes peace when she is in the same room. That is the only thing I can think of that has changed.
I will definitely make an appointment with the vet. I will let you all know how I get on.
Many thanks for the replies.