My best friend is a totally different person after high school. What should I do?

I think that you're right people change and sometimes we just drift apart from people even if we're really close to them before. I used to have a best friend too, who I felt was the only person I could really trust and talk to about anything under the sun. But then it came to a point, that we had to drift apart. Its normal because you meet different people and you're always on the process of discovering yourself. And so right now after college she probably evolved to someone else, and you have as well. And I know at first its really hard to think that you have to move on, cause you're thinking of all the memories you had together and how she's the bestest friend you could ever find. But then, if its already clear that she's not really making an effort to want to be your best friend anymore and she's found a new set of friends.. Then probably she really has changed. Its not such a bad thing, cause maybe this closed door will lead you in store for something better. Who knows? You're two different people now. You can stay friends of course. But then as far as "best friend" goes, maybe this is just a sign that you should go on and find someone who will treat you as a best friend too. :)

You accept people change. Sometimes for the best, sometimes for the worst.