The transition from child to pre-teen is a period for exploring our independence and establishing our position within a group. We learn that there are patterns of behaviour which are likely to make us popular or accepted. During this time, we are focused on gaining the approbation of people in our circles of influence, including family, classmates and teachers.
Your daughter is adopting behavioural traits which are dominant and successful in one of her social circles and applying them to other situations. I am guessing she is oblivious to the damage her comments are causing to her family.
Studies into the developmental patterns of pre-adolescents have established that, in conflict situations, boys are more likely to be directly verbally or physically aggressive, whereas girls use indirect aggression.
When used deliberately, the snappy put-down or cutting remark can be a way of gaining dominance or admiration.
Habits spread like wildfire in schools and it is possible your daughter has seen friends using this technique and is copying it. The problem with these types of comments is that they may be superficially witty but can fracture relationships.
