that right there (she being selective on who she does this with) shows she understands its not acceptable behavior but does so because she is allowed to do it with you, her mom, her grandma and you. children are very perceptive and figure out very young who they can get away with what. its up to you to set the boundary where you want it with her. thats what care takers do. the first few times you tell her differently is hard but after children get used to the rules and boundaries of others they are fine and even behave better in general for it.