Is this flirting? Or is she just being immature?

So I just met this girl at a party two weeks back. A couple days ago she invites myself and a friend over for a movie. Throughout the whole movie she keeps tickling me. I am ticklish. She says I make constipation noises. And thats becuase im trying to hold back from laughing(im all skin, bones and muscle. Not too much fat on me) And she keeps doing it. Shes 17, almost 18 and still in high school. Im 20, almost 21. What is she doing?