I'd want dd to broaden her circle of friends. Sounds like one if not both these girls are a bit silly and unreliable. Girls generally seem to want a bff and not be too comfortable with threes and get silly and insecure. Tell dd to rise above it if she can.

My son and DIL are both primary school teachers and would tel you that this is absolutely normal with the girls' friendship groups. My DIL is often having parent in worried about girl A being spiteful to their DD and then girl A gets girls BC and D to be "against" DD and can she "keep an eye on things" - she is an excellent teacher and is very popular with the children, but she has to tell the parents that girls are like this, and the best thing is to let them sort it out themselves. My son says the same.

They have a daughter aged 12 and is now at sec school but when she was at primary there was a girl who was very possessive of my grd dghtr and made her life quite miserable because she was afraid to stand up to this girl and told me once she had to "fake" being her best friend - this was at about aged 7! I am I know over protective about my grd dghtr (only cus I love her so much!) and I used to ask my DIL to maybe have a word with the teacher or the other girl's mother. However my very sensible DIL said that was not the way to go - the thing parents should do is teach their children the skills to deal with these sorts of situations, as they will arise in one way or another through life.

SO yes secondary school will mean new friendship groups. My grd dghtr goes to a school none of her primary school friends go to, and she is on the shy side, but has made friends, but she talks of one girl in the class getting a little gang of girls around her and they only talk to each other, but then one of them leaves the gang and the friendship groups re-group. I think it's a girl thing!!