Encourage your teen to go to the 1st night teen meeting, even though she'll tell you that it's for losers. That's where all the teens go to check each other out and to complain about how lame the program is -- but by the end of the stupid games, she'll have met several other teens and will start to hang out in a group. If she doesn't meet other kids that first night, not to worry. There are always nice teens who try to draw others into groups when they see them alone, and sooner or later she'll connect up with a group. Our teenage boys (soon to be 15 & 17 -- we're crusing on Glory in August) always meet new friends on our cruises. On a Spring Break cruise, the ship will be LOADED with teens.
The kids are allowed in the disco before 11:00 (sometimes this varies) and then are supposed to leave. Depending on the ship & security, sometimes they're allowed to stay. Often they find a quiet lounge or hallway, where they congregate, or they eat ice cream & pizza all day, go to the shows in groups, play video games, and just "hang." I don't think the teen activities are usually well-attended, except for karaoke. By the end of the cruise, they're usually frantically taking pictures of each other and exchanging e-mail addresses.
You might suggest to her that if she finds a special friend or group of kids, they should go ahead and get formal pictures taken as a group when the photographers are set up -- why not? The photographers are used to it, and either you or she may want to buy one as a souvinir (sp).
Have a great cruise!