Everyone had or will have an experience like that. I had several ones. It hurts, I know, and mostly while we are depressed, it is the end of the world. However, in reality, it shouldn't be, this is part of growth, and trust me, when you reach my age you are going to laugh about it. She rejected you and I understand that you miss her friendship as well. But there are +7bi people in the world and time heals. This pain that you are feeling now eventually will go away, I promise you that. I lived that before. It's worth it waiting, it will get better. Man up and move forward! You want to be alive, you are here for a reason, no?
No happiness or sadness lasts forever.