Half Awake & Half-Asleep Dreaming?

I am half awake and half asleep when I hear Millie meowing. She sounded like she was in the closet in the hallway by the door. I tried calling Jackie, and she did not answer. I tried calling Deb. Then I decided to turn on the light. I looked at the cat tree and there was Millie sleeping in the hammock of the cat tree. Ok, why did I hear Millie meowing?