One of my best friends has been really distant lately?

Me and my best friend Angela have been best friends since we were little kids, and I always considered her more of a sister than a friend. I have many close friend, but she's always been the one to be there any time. Well, when I met her, she was friends with a lot of people that I didn't necessarily like, and I had learned to live with that, put up with these friends. Well, now, she won't even talk to me when she's with them, and it's bothering me. I feel like I can't even talk to her about anything anymore. I've tried having real conversations, but she says she's always busy. And when she's not busy, she's not in the mood and just wants to read. I would say it's her that's changed, but I'm starting to think it's me. I know I've grown up a little(especially because of things at home), and I feel like I need someone to realy talk to, but conversations with her always turn into unimportant stuff. Also, lately, her little quirks that I've always loved have really caught my attention, and just some of the little things she does starts to bug me, but then I feel really bad because I can't talk to her. I don;t think she realizes what's happening to her, and she's all of a sudden starting to get hurt becuse I don't know how to act around her naymore. Please Help!<3 I don' wanna lose my 'sister'