Question Author
Well this "thing" took an interesting turn.
Her teacher called me up just before I left for school to apologise for last night and to make sure I didn't take it the wrong way. I've stated that I will address it at home, however I was still reluctant for her to embarrass my daughter in class by pointing this out to her. She's assured me that she wouldn't do this anyway, she'd point out "babyish" behaviour in general to the whole class, and that they shouldn't be now they're in the juniors, etc etc.
She also assured me that MB's a great little girl in class, very very bright and she'd hate for me to think she personally disliked my child, or parts of her character.
Upshot of it is that we've come to a sort of uneasyish truce about it- lol.
Mind you, after talking to a few other mums in the yard, she also peed those off too- so im not on my own.