friend rant

I have this friend. I consider her to be one of my best friends. Recently though, she's been hanging out with these other people. At first I thought nothing of it as people are allowed to have other friends. Recently though, I felt excluded. I haven't hung out with the friend in 3 weeks because she was always with her other friends. Whenever i'm with her and those other friends, they'd be secretive around me and disclude me. They once went to a party and sent me snapchats of them at the party. They have each other's names in their instagram profiles. I probably sound really petty right now.. I feel like she replaced me completely.. I talked to her about it and she denied it, but honestly, i'm not convinced. What should I do now?