Irritating immaturity

C: new friend has a close friendship with a woman I dislike
T: no idea-
F: jealousy/insecurity?
A: complain to husband, criticize this other woman, obsess over how they can be such close friends when this new friend is so very different to the woman I don’t like, feel jealousy when I see their interactions, feel ashamed that I feel this way and wonder why I am being so childish
R: I dislike myself?

Help! I cannot fathom why they are friends and I cannot fathom why it bothers me- except that now I have a lot more interaction with the undesirable acquaintance given I’m in a new social circle. I also feel competitive. I’m 46- what a joke!