Inspired by another thread on AIBU, as I have a similar problem (blatant cut-paste of some bits from other post, since situation is so similar).
Background in short:
DD has a friend whose parents we have known for a long time, and so both girls have been friends since they were babies. They went to different nurseries but since reception the same school and class.
All through reception we had issues with friend hitting, scratching, biting DD yet still playing only with her, and not allowing DD to play with others. Similar to the other poster's experience, she would hurt DD if she tried to play with others, vice versa if others tried to play with her.
In year 1 things became better when I urged DD to walk away the moment the other child started hitting. So friend has now changed tack. She is now all over dd as soon as she walks into the classroom, hugging her, holding hands, drawing little pictures and so on. I would normally say 'awww' but DD is naturally outgoing and always had lots of friends in nursery. The friend is not very well liked so gradually other kids have been giving these two a wide berth. So it's turned into a mutually dependent relationship now. Moreover friend is not a very well behaved child, and dd has started copying her, esp when they are together.
I have spoken to their teacher but they are not much separated in class, as she prefers to let kids make their own choices at certain times of the school day.
I have watched them together at parties and when friend is around it's just those two - I have seen her pull dd away from other children if she was playing with them.
I don't like them being friends at all but it's hard to explain this to DD, who is overwhelmed by all the attention. I try and meet friend's parents as little as possible outside school.
The problem now is that my DD is becoming insecure about herself. She says "I am bad that's why she hits me", "She makes me little drawings, so I have to play with her".
Sorry for rambling on. How do I teach a 6 year old to deal with this?