I feel like a third wheel?

I'm going to the mall with my best friend, but she asked if she could bring her other friend. I said sure, because I know the girl to but lately I feel like I don't matter very much anymore.I mean when we go out with friends, she ignores me. Idk, what do I do? We've been best friends since first grade, and we are in middle school now. I think it might be something to do with me, to be honest. The last few months I've been being different, like I'm more"scene" or "emo"? Ever since that started happening(I didnt even notice until a bit ago) she started acting like me more, copying me. Idk, what do I do?