"Uh oh, here come the dreaded friendship wars." This is what most mothers think when their daughter comes home for the first time crying because a so-called 'friend' was mean to her. Indeed, most of us can remember only too well how complex and painful girls' friendships can be throughout childhood.
"It's also one of the first signs that they cannot control the world for their growing daughters," adds Terri Apter, author of Best Friends: the pleasures and perils of girls and women's friendships.
Besides feeling protective (should I call the girl's mother?), mums may find themselves wondering why their daughters put up with it in the first place (why doesn't she play with more boys instead?).
But Apter explains that by the age of four, girls and boys tend to segregate themselves when they play with peers and when they form friendships.
"Girls choose girls; boys choose boys. If boys try to join a group of girls, they usually mean to cause trouble. If a girl tries to join a group of boys, she is very likely to be rejected. This segregation seems to be universal - across culture and class, and occurs - especially in a school context, even when the adults try to mix the children."
Distinctive cultures emerge in these all-girls groups and in all-boy groups, she explains. "Boys are more physical in their play than girls, and engage in a good deal of rough housing. They form more obvious, and more stable, hierarchies, and engage more directly in competition with one another."
Girls, on the other hand, are more likely to sustain long, turn-taking conversations. "Girls are also more likely to express agreement with a friend's suggestions. When they make suggestions of their own, they often add a tag question such as 'shall we?' or 'should we?', whereas boys are more likely to use direct imperatives such as 'give me' and 'put it there', or prohibitions such as `don't do that', `get away from that'."
The conflict in girls' groups is therefore much more likely to go unnoticed, says Apter. "The competition is for the more nebulous good of popularity (not, as in boys' games who can throw furthest, who's the strongest). It's about who is best liked, who's most likeable, or popular, or who is closer to the girl whom everyone likes."
The chief commodity in the girls' community is intimacy, she explains. "Girls monitor their friendships for subtle shifts in alliances, and they seek to be friends with popular girls."
But mums shouldn't be too quick to be relieved if their daughter is the popular girl, warns Apter. "Popularity is a kind of status, but it also brings problems. Popular girls are often disliked because they can be envied and they can be the target of gossip. And because the most important thing in girls' friendship is intimacy, they cannot have masses of friends, and so a popular girl, who attracts lots of other girls, must reject some of those girls in order to preserve the intimacy in the relationships she has. This makes her seem to others stuck up."
Popularity is dangerous for another reason too – it is transient. "Girls' hierarchies are much less stable than those of boys'," she explains.
All this this makes it hard for parents to give their daughters the advice they'd like to, says Apter. "We'd like to say, "Stay away from her if she's mean," and "You should just ignore what she says," But such advice, in a girl's view, is a sure sign that we don't understand anything.
"What we can do is provide support so that they don't suffer that awful shame and isolation that can be an outcome of girls' friendship wars. And we can also pass on to our daughters the skills to assess a friendship themselves."
Gaynor Sbuttoni, educational psychologist specialising in emotional issues, agrees. "It's so easy for parents to jump in and say, 'Right, well she's never coming round for tea again.' But actually responses such as, 'That must have been difficult' or 'I'm sorry to hear you are feeling so bad' are much more constructive because they acknowledge the feelings your daughter has. Then together, you can work out ways to deal with this particular situation and to empower your child in the longer term. It can be useful to do role play with younger girls."
Educational psychologist Karen Majors adds that there has been some interesting work in Denmark around the concept if discouraging 'best friends'. "The girls in one particular school that has featured on Newsround are encouraged to have good friends and special friends, but not this exclusive one best friend and so far, the outcomes look good. Perhaps this is something parents could learn from."
Majors also believes mums have a role to play in using their own friendships to convey the importance and value of friendships in life, as well as revealing how friendships have to be worked at.
10 top tips
Find quiet times to talk to your daughter about her friendships and see these chats as a way of building up trust, so that she feels she can always open up to you if things get difficult.
Never belittle how she feels and give her the space to talk about the seemingly little things that are bothering her.
Watch how she acts with her friends to help you give her constructive advice on how to deal with challenging situations.
Don't jump in and take over – empower her to find ways to deal with friendship difficulties herself
Reassure her that falling out with friends happens to everyone at some point.
Sometimes just sharing her problem with you can help her deal with it better the next day, so don't be hell bent on finding solutions every time.
Help her find ways of boosting her confidence, so that if there is a crisis, she's ready for it.
Be prepared to have some intimate chats around bedtimes – this is a common time for girls to open up about friendship troubles.
Encourage your daughter to form various friendship groups, for example via activities outside school.
If it gets really bad, talk to the school, growing numbers of which accept that if girls are unhappy, this can stop them learning.
More on Parentdish: Mean girls and school bullying