your cat is kneading, they do it when they are kittens to their mothers stomach as they are nursing to help with milk production. when they do it to people its a loving, comforting gesture. some cats dont do it after they reach adulthood and some keep doing it. i have two cats, one does it all the time, to blankets, pillows and my boyfriend and myself. if your kitty is doing it to you it means she loves you.