I think my 'friend' only likes me because...?

I think my friend only likes me because I actually have a brain... not to brag... but to me it is so plainly obvious that she wants to be a the top of my best friend list. She constantly tried to be with me before I got to my best friend. Like in PE cl today, I can just feel her quickening her pace to get to me before my best friend and I partnered for the push-ups and sit-ups and I don't want to be mean so I say yes. I admit I might be slightly obsessive with my best friend, but I'm not over the top. Whenever I see my friend I walk to her, and immediately raise my voice to say her name and direct her to where I'm standing. But now, my other 'friend' says it with me, and I can sort of feel the fake-ness. I think she just wants to be my friend because of how my teacher praised me with words like "the great" or "queen of math". Which was actually kind of weird, because my friend is equally as brainy and never got the praise. The praise got to the point in which I tried to avoid speaking in cl, and she (my teacher Ms. Shukuya) created an enemy for me because of others jealousy. It was nice at first, but then it became horrible. My 'friend' Emily, has been following me around ever since. I feel sorry for her, though. She tries, but my best fiend Samantha will always be at the top, because she helped me through a tough time. And, I am a nit proud of my grades, because I do not try and I have A's, but I don't broadcast it. Today was the first day I refused to do something Emily wanted to do with me. I want her to lay off, because it is too late. Sam was there in my crisis, not her. But she's still a really nice friend. When I try to play along with Emily, I brag even though I know it is bragging and making Sam more wary with me. But I want Emily to know that I know what she's trying, and it is not working, in a nice way. What should I tell her?