My stepson started to get "mouthy" when he started school too. I think it has to do with them trying to become more independent. He is almost 8 now, and still has his moments, but has improved. Time outs helped A LOT!!! One minute for each year of age. If he was being disrespectful he would sit in time out for 5 minutes. At my house this was in the kitchen, because the kitchen is b oring and has no toys. He would sit at kitchen table and I would set timer on microwave. When it beeped I would ask him why he had time out and he would tell me and we would talk about why it was wrong and then he would go play again. Just set limits and enforce them and she will grow out of it...kind of.