Spayed or not???

Question
I have two totally indoor kitties.  Sadie is almost 5 years old and Olivia is about 3 years old.  Both were spayed once they hit about 7 or so months of age.  Sadie is fine, but all of a sudden, Olivia is acting like she's in heat!  None of the incessant yowling yet, but she seems headed that direction.  Why would a cat do this if they have been spayed for over two years now?  

Answer
Hi Julie,

If she had ovarian tissue missed by the vet in the spay she most likely would have displayed heat behavior earlier. What exactly is the behavior she is displaying? Some cats as they get older get more affectionate. I need to know what she is doing before I can really help you. Please write back.

Ciao, Karen