Brother broke up with his girlfriend

My brother and his gf broke up on Saturday (it’s Tuesday night as I write this) and it was seemingly mutual but also mutually devastating as there is no resentment just sadness that it could not work / was not working. They started dating spring semester of senior year of college and she was his first girlfriend. I was a sophomore and we all went to the same school so even from the very early days of their relationship, we all became super close. She was there when my mom passed of breast cancer last year, someone I reach out to frequently for the most random things, advice, and updates on any and every aspect of my life that she basically hears about as if it’s an evolving news story. She is also very well integrated into my extended family dynamic, where I have 3 boy cousins all around the same age as my brother and I, and my cousins gf, who made for a trio with myself and my brothers gf as we were the only girls. They have quickly become some of my best friends and I had no doubt they’d be in my bridal party. Last year we all went on a family trip to Turks and Caicos and this past summer was a cousins trip to Barcelona that we all paid for on our own because we’re genuinely close and wanted to and had the BEST time ever. Anyways, she’s really close to me and my family and woven into my life in a way that often feels so far disconnected from my brother. Now that they’re no longer together … I am distraught. My brain is convinced she is dead. I had the thought to myself today crying driving home from work that it’s okay because she’s in a better place. WTF. Her mom reached out to me saying she’s distraught. I checked in on her via text and she made it clear she is “lost and sad and confused” and clearly miserable. Our texts were so formal and weird and careful in a way they never have been before and would’ve been so out of character for us even just hours before their break up. My loyalty is obviously with my brother at the end of the day but I don’t know how to grieve a loss that I have 0 control over, when it’s not even about me, and when it’s someone who is very much alive and (kinda) well, and not just gone forever (which Thank God for that but still - it’s moreso like you’re there you’re healthy you’re living your life… so come be apart of mine again…) Ugh what do I do. I miss her sm and it’s only been a few days.