Some years back, I was friendly with one of my neighbors who had a large friend circle - she was close friends with this other woman who for reasons only known to herself started pulling this friend away from the other friends - it's like she became very possessive and it didn't matter that it was obvious - over time they separated and formed their own group -

I've seen this happen in college too - where one person completely claims the friendship of another and sort of isolates them from the rest

Just musing here....

Btw I almost missed this post - no notifications unfortunately