My cat is a female , just one year old and recently she has become very quiet, not wanting anyone to hold her, she's not playing with her toys or us like she use to, she just lays on the floor, I was thinking it's the heat so I put her in a air condition room and she won't stay. What am I doing wrong?

We would like more information in order to begin to provide any sort of helpful answer, if you would be so kind...

I presume she has been spayed, if not, that may be the source of the problem.
Is she a strictly indoor cat?
Is she eating normally? If not, does she eat at least every other day?
Has there been any change in the daily routine in the home lately... a cat is an animal that likes things to stay as they have been... no changes to have to put up with.

Thanks for the additional info, in advance.