Girl punches the **** outa my back?

so ive liked this girl for a while and thinks she might have a thing for me but im ina casual relationship while shes in a casual one too. this girl will sit there and we play when we see certain cars we punch eachother just the guys tho. she will only get me and get me as hard as she can. i dont think she hates me because we chat on facebook im alot and she laughs at my dumb *** jokes but her body language is weird talking to me whats it mean