My bestfriend is trying to be cool and popular and its getting very annoying?

We always were super close in school but at the end of school she started leaving me behind and ditching me and going to class with other people she never hung out with before. Then i brought my friend a gift because she was moving away. The next day she did the same thing? Then she was planning a party and she literally invited the WHOLE 7th grade and she didnt even know most of the people and she basicly ignored me most of the time I was there. Now that its summer shes doing all this stuff with people and posting it everywhere and shes not evn inviting me. Shes ignoring my texts and skype messages when shes online. She hasnt even said hi to me since before school ended. Im so confused.