I wonder if the dobbing is a whole perpetual cycle?
I mean, if she dobs alot and the other kids/parents shy away from her, then she may have resorted to dobbing to get attention. They do say that negative or positive, any atetntion is good.
Does she have many friends?
May be you could have a play date over for her adn somehow bribe her into not dobbing and when its all over, explain to her that people will feel much nicer around her if shestops dobbing.
Hope the poor lil bugga isnt lonely.
Hugs to you too, we all lose it sometimes, dont beat yourself up. xxx