The 6-year old challenge

My child is a 6-year old challenge. We've been having quite a bit of back talk from her, general not listening and a lot of hot flashes. Well, it all sort of came to a head when we spent a good 10 days with the family. The cousins, there are two that sort of flank D on both ends - one is 6 one is 9. Both girls listen quite well...and D doesn't so much or at least she hasn't been lately.