Just a thought- but it sounds like this girl is seen as the "naughty" member of the class.... so everything she does is reported to you...... If they see her as the naughty one, then they aren;t the naughty ones.... it feels better and makes the others feel in the "in" crowd.
I observed a boy in my daughter's class when she was in primary school. He was considered as "the naughty boy" of the class. He was very able. He got told off a lot (for pulling my daughter's chair away once) and he was sent to the head etc when tiny. He really was labelled the "naughty child". I watched the teacher (I helped out)... evrytime he wriggled, flicked pages in the book "XXXXXXX please sit still, how many times do I have to tell you.... put your pencil down...." etc.

He was then diagnosed with aspergers and the teachers treated him differently. Much of his odd behaviour was ignored (and the rest of the class' attention not brought to it). Different strategies were used by the teachers (and as a teacher myself... they did really well......I don't know how they ignored some of his silly noises). When the children sat on the carpet, he sat at the back and if he wandered around, no-one saw. Within a year, my daughter no longer saw him as a naughty boy but as a child who was good funny . It's amazing how theteacher's attitude changed everything!!!