Because of the timing of the song (the album that it came out on) I think it was likely written when Paul was facing the potential split/divorce from Heather. I think it's a commentary on the corrosive effect that some of her friendships had on their marriage, and how she seemed more focused on them, than him. Thus the sense of isolation as noted by others. The style of the song does reflect George's musical style and sometimes vaguely caustic lyrics and I think that was what Paul was referring to.
Because of the timing of the song (the album that it came out on) I think it was likely written when Paul was facing the potential split/divorce from Heather. I think it's a commentary on the corrosive effect that some of her friendships had on their marriage, and how she seemed more focused on them, than him. Thus the sense of isolation as noted by others. The style of the song does reflect George's musical style and sometimes vaguely caustic lyrics and I think that was what Paul was referring to.