It sounds as if there could be an issue from home maybe as there is a new Baby in the House even though she is good with the chile she feels some lack of attention the Baby is getting, how about giving her more one to one time Get her Dador other Family involved and more activitys for her.I dont think you should be discussing her behavior with classmates that is not kind as it may make her feel embarressed, it is belittlring to her., the Teacher probably has got it right, back off a bit and let it go, she needs to get her self Esteem going and this wont do it.