I've been seeing my brother's best friend for about a month now and I've known him for like 5 years. He has a little girl who's 6 and I met her when she was like 3 but back then I was just his best friends little sister. And I'm supposed to meet her this weekend at his birthday party and I'm really kind of worried, because I wont know many people there and I dont want to be awkward, I need advice.