I am so drained

I have this bestfriend since 2nd grade. We've always been classmates until this year. She's always been my comfort person. She's like my sister. This year we are not in the same section. I have social anxiety. Im having trouble with socializing and making friends. Luckily I found some friends. Until now I still see her as my bestfriend. But her? I'm just now her second choice. I saw a her post with her 2 new friends. She didnt even informed me that they're at the mall. She's now cold to me. I'm giving her all of myself. I'm the only one whos making effort. And the other day, I was so mentally drained. She said something that has offended me bad. I feel like harming myself that time. That's just a few of the shitty thinks that she's doing to me. I cannot defend myself. I dont know whats happening in my life. I just feel like giving up.