Just got back from 5-day Enchantment cruise and loved it. My daughter is 13 and she really liked the teen program. One catch, you have to want to meet new friends. On the first night they will have a teen "meet and greet" session - an absolute MUST for her to attend. She will feel really awkward going since she won't know anyone, but by the end of the session she will have a dozen new "best friends," I promise. My daughter was nervous going, but after that first session we never saw her again... not really, but she was very busy almost all of the time. She did kareoke night, disco night, pajama movie night, scavenger hunt, the "Quest" game - really fun, "hottie hunt" - also really fun, rock wall climbing, late night buffet runs, and miniature golf.
We saw lots of teens wandering around the ship, getting into trouble because they didn't participate in the program. She won't regret it if she just goes the first night. Also, get her a disposable camera of her own to take pictures of all her friends.
Book your excursions online at the RCCL site, they fill up fast and if you wait until you get on the ship there's no guarantee that you'll ge the excursion you want.
Let me know if you have any other questions.