pwwalker,
I have a DD-13, DD-10. DD-13 will be happy to hear there will be another girl close to her age. Are you planning on going to the 411 in the common grounds the first night? I hear this is where you will meet others on the cruise your age. I told my daughter she should go (a little reluctant and shy) so she gets to know others her age on board. She sure does not want to be with her younger sister!