My friend has passed away

I M[17] have a close friend F[17] who has a birth defect of some kind idk what it’s called. She came to my school two years ago, and she backs my closest friend. I shared everything with her and opened up only with her. A month ago she was hospitalised due to a small heart attack. She was in icu for about 3 weeks, then she was transferred to rehab. She lost her voice, couldn’t breathe on her own, had a catheter attached, basically had the worst living quality. She got depressed because of the drugs, but she got alright again. On Saturday, 8 Nov, my message was left on sent after I replied to her 7 mins late. I got worried. Yesterday, our headmistress called us to a hall and said that she had passed away. My world had crumbled. I can’t stop crying, I think I’m going to ruin my prep, idk what to do.