My best friend

Okay so, My best friend who i know for 6 years now had a fight with another friend (let’s call her tiffany) of hers she backstabbed my best friend and talked shit yk..
But this school year tiffany ended up in my class and i became friends with her. Fun fact: I always wanted a big group of friends since i was always bored and had nothing to do. I got a text from mu best friend today saying that she doesn’t want tiffany around her, i mean that’s okay but i can’t just shoo her away every time that i come near my best friend to talk to her. So i told my best friend exactly that..She got mad and said if I couldn’t do that I didn’t have to come near her at all at school..I really am hurt that she would make me choose someone like this..and even more hurt now that she knows that i always dreamed of a big group of friends..this is the first time we had a real fight (argument). But now i feel like she doesn’t like me anymore and I don’t know what i should do…I can’t sleep..i cry all the time..i’m worried every second of the day.. if anyone could give me even a bit of advice that would really help me..thank you in advance