We did a Princess Mediterranean cruise last August, when our kids were 13 and 18. It was a fabulous cruise and our best family holiday yet. Meeting other people her age was a bit of a problem for our daughter - fortunately I had hooked up online with two families with kids her age (both boys!), and she hung out with them, but it wasn't until almost of the end of the 12 days that they found out that there were quite a number of 18-20 year olds on board. They are at an awkward age - too young for the disco and too old for the teen program. She had a great time anyway, and wouldn't have wanted any organized activities, but I wish that Princess had just suggested a meeting place the first night for similar age people so they could have found each other. I have heard that other lines do this.
Sheila