Yall i need a relationship advice

So ik this is mangago BUT still i just need to talk with someone. Sooo I was best friends with a girl the whole summer untill january bc then she started to act offputting to me. I kinda made some distance but still wanted to be friends. She doesnt matxh my energy but i still like her in some ways. We are class and seat mates but she doesnt go ro school like at all ( mostly going striking bc enviormental activist or goes on concerts) but yea. We have a distance and now ima have my 18th birthday whoch is like sweet 16 in my xountry but she told me she wont come bc itd be the best for us both We literally didnt talk this time, I started talking to her abt it but she was like geah we just drifted apart. Okay but like- Why wont she want to celebrate a huge part of my life.. I kind of get it but still.. Im hurt bc i rly valued her, bought her things, took her out and shit, introduced my friends. Idk what to do and how to react