@jazz687 OK OK OK,forgive me for doing this.
But I kinda have an experience.
When I was in first grade,I really liked this girl.But when she started hanging out with another girl,I felt really upset and sad because she was the second friend I ever had.When she didn't't come back to hang out.My sadness turned to anger and vengeance.So I got revenge on the boy by putting some snails in his backpack.The kid was super pissed!But luckily,no one ever found out who did it.And a few days later, the girl came back and we started hanging out again.
I think my story proves that if you give them some time,maybe the other girl will figure out that she can trust you with your friend and that maybe she shouldn't have been so hasty in her previous decision.