A bit of background: DD (Yr4) is quite confident, but also sensitive and kind. She does not have one particular Best Friend (though she often says she wishes she had) but instead is a largely part of a group of 3. The other 2 girls A and B have been friends since babyhood. DD joined the school in Yr 3.
Both A and B have been over for play dates. Both seemed lovely girls, polite, friendly, lively but generally well-behaved. Friend A is a stronger character - likes to lead games, can get upset if things are not going her way. Friend B is happier to be go along with others - a bit quieter and less likely to get upset.
There are often issues in threes and DD has come home feeling upset at the behaviour of Friend A (stronger character). She has described situations where A has said unkind things ( eg "You are a stupid idiot") or taunted DD. Or A has blanked DD and gone around in a strop for an afternoon. These incidents often seem to happen on the days when DD and B have a shared extra-curricular activity. I think A is jealous/feels left out and is lashing out. Friend A tends to hit out (so to speak) at DD rather than friend B and DD often ends up having to find someone else to play with.
These instances happen bad enough for DD to tell me about them almost as soon as school is over about once a fortnight. I think I can tell from her behaviour/how she treats her little brother that they happen maybe a little bit more frequently than this (but not as bad) maybe once or twice a week. However, the instances do tend to be totally forgotten the next day and everyone is best of friends again.
There was a run in today though and DD is feeling very vulnerable/upset about it. I think she is tired of having to tip-toe around Friend A, about the flashes of jealousy. I have talked stuff through with her and am trying to help her deal with this. I do not want to say just ignore it. I got told that crap advice as a kid and it did me no favours what so ever! So far I have
- Made suggestions that maybe DD needs to work out if the whole group is worth it if one of the people is not a good friend. Or indeed maybe B is not such a great friend if she lets A be mean. Got DD to acknowledge that she is worth more than that and she does not have to put up with rubbish behaviour from anyone - particularly not so-called-friends.
- We have role-played a few come-backs for her to use if Friend A says something mean: "Did you mean to be so unkind?" "How would you like it if I said that to you?" "Meh...what is your problem?"
- DD and I have agreed that at the moment Friend A is "winning" - ie Friend A gets jealous - hits out verbally (or with silent treatment) to DD, DD goes off to play elsewhere...ergo Friend A has got what she wanted - B to herself. So DD knows she has to stand up to A. To say something. To stand her ground.
- DD is worried - actually no - scared - that if she answers back then Friend A will go running to a teacher/Lunchtime Supervisor and the DD will end up being told off. DD is the sort of child who hates being told off - will do everything the teacher says, compliant, helpful and has been told off so rarely that if it happens it devastates her. I have said I will talk to DD's teacher - not to get DD"s teacher to deal with Friend A, but to let her know there is an issue, that DD will deal with it following our role-plays - but I think teacher needs to be aware in case anything kicks off iyswim. If Friend A does cry to the teacher.
Btw I would like to apologise if my description of Friend A is a little unsympathetic. She can be lovely - but several times in the last few weeks she has been the cause of upset for my DD and the deep primal part of me does want to go up to A and tell her not to be such a nasty, bossy possessive cow and worse language I shan't of course. But quite honestly, right now I don't like her.
This has been going on for some months now. We have role-played the come-backs before but DD has never used them as everything is always OK again the next day and then DD loses courage. But I think she is getting sick of the yo-yo. As above - it is only the odd occasion and the next day everything is OK again. DD said the word bullying, I said it was not really bullying but it was absolutely unkind behaviour, not acceptable from a friend and needed dealing with. Am I minimising this? Or Overplaying it?
Should I be going in and asking the teacher to do something more? I really would like DD to learn how to stand up for herself now, as I think it will be invaluable going forward.
Does anyone else have any other suggestions on how to help DD?
I am sorry this is so long - she is my pfb and I want to make the hurt go away. 
(Oh and am aware have only heard DD's side to the story but the repeated nature of stuff seems to stack up a bit of evidence of something happening)