Please Help me With Friend Problems

Before we start a little about me; Hi ladies you can call me Mouse, I've had issues keeping friends for forever, I struggle with my identity and only just recently have I found something that makes me feel a little bit grounded (wearing a bandanna) I'm fiercely loyal to the people I care about and I'd do almost anything to protect them. Okay let's get on with this shall we.

So I have this friend, we'll call her Summer, she's my best friend and she's like a sister to me. But recently we've been growing apart. She has another group of friends that she splits her time with, switching between them and my group. That other group includes my ex who she's now really tight with, the girl she's crushing on, my friend since childhood, my old elementary school friends and a girl who she wore matching sweatshirts saying "every short girl needs a tall BEST friend" and vice versa. She's been acting cold and bitchy to me for about a month. She's been wearing a bandanna for the last week even though she knows about my identity issues and the meaning my bandanna has to me. I worry because the Pops (the popular kids) like her and are buddies with her that they'll start wearing bandanas making my thing an old trend. The rest of my friends don't understand why I'm upset that she's wearing bandannas, they think I should take it as a compliment, I don't in the slightest. What should I do?