I had a similar scenario that happened to me too, group of friends, but two of them who were best friends were having conflict but none of them would confront one another, there was obviously issues in their friendship was that crumbling. One of my friends came close to her best friend, cause her friend prioritized the heck out of my friend, and basically forgot her original best friend existed which pissed off that friend.

When we were on the bus, that girl's best friend wouldn't give her any attention just my friend. I tried doing everything to break that tension between everyone and make her feel included, but no matter how hard I tried, it was if that friend was doing it on person.

Soon as we got off the bus stop, yup, never the same since. Problems rose, everyone snapped, months later, done. Now none of us talk, besides me and my original friend I knew despite us all being close.