Does this girl like me?

Ok theres a girl i like and i want to her ask out but shes my bestfriends sister and we r friends but not close and i dont want to make it akward. I sometimes catch her looking at me, she always laughs at my jokes, she always calls me ugly but playfully and smiles she wrote me on facebook and said "hey ho u should add me" but thats it she texts me sometimes but its never about us and the other thing is the other day at school i saw her in the hallway and she stuck her tongue out at me, do u think shes into me?