If she is in heat it's a shreaking cry. I relate it to a howling sound. You'd think someone was torturing the poor kitty. I would say if she is just mewing crying when she sees or hears you it's a lost or dumped off kitty. I would summarize in my mind. If the kitty doesnt have a collar with tag on or microchiped I would consider it mine I would probably not let it out and about just incase if it's in heat your likely to have kittens soon down the road.