Is my bestfriend trying to be me?

I need to address two things before I answer your question.

1
I like how you use "best friend" as a compound word. I think it works better like that and conveys a good meaning. Kudos

2
I also like your backward smileys.

Now, here I go
As best friends, of course there are going to be many similarities between you two: who you hang with, how those people dress, what you eat, what you do in your free time etc. You guys will also share with each other much information about what you are thinking, providing almost unfiltered information to one another. I would be highly surprised if you guys were different.
The clothes, and all make sense, and Could be written off as her trying to be like you.

Now with this in mind, as far as the men are concerned.
While it may be possible that she has the same tastes in men as you do, it would seem like she is simply following suit. I believe that you have the rights of saying that you claimed the territory first, and that she needs to back off.

She is trying to be a good best friend though. Don't hold it against her, and don't lose her. You will much appreciate her after High School.

Well you can look at it from another angle. Maybe your friends because your so alike. I know that with some friends of mine they mistake us for twin or brothers even if we don't look much alike.