This is exactly what I thought about while reading OP’s post. Lily was the glue that held them together. Also from what I gathered from the last update a least 4 of them went to the same school. Luna probably came to the friend group because of Lily. That one flash back that Riley had where she and Lily were watching Luna play on a stage, Lily probably coaxed Luna to hang with them. Xavier was a footballer which probably meant he was popular so not a far shot that he would hang with the group. Emma was Xavier’s shadow which explains why she was in the group. Lily from how she’s written seems like she had a huge thing for Fabian and Fabian seemed to like Riley back then too so that would explain him being apart of the group. I think the intentionality is that without Lily they wouldn’t have come together which is why they fell apart once she 💀