My 15 has been doing it for years and loves it. Autographs and photos, as many characters as possible. We actively figure out how to meet as many as we can. However, if she hadn't been doing this on her 10 trips since she was 3 years old, I don't think she would suddenly pick it up as a teenager. It's probably best just to ask the teenager. But make sure knows, she will not be the only non-child doing this. Lots and lots of teenagers and adults, both genders, wait in line to meet characters.
One of my favorite memories from last summer was my 15DD talking my 12DS into introducing himself to Pocahontas as John Smith. It was so much fun. He was so deadpan with it, she looked actually confused. The character handler asked me if it was really his name.