You should go for a walk to see if she is around. Sometimes a cat will get spooked and climb up a tree for safety only to get stuck up that tree not knowing how to get down. That is something I happened across when I was working in my yard and began hearing this cat crying. It had climbed up a tree and could not get down by it's self. Someone eventually had to help that cat down. It happens more than people realize. And it may even hear you calling but it can't come to you because it's stuck up in a tree.