Given her age and what she see's (friends have) Beats are what she points to. I'd rather get her a headphone that sounds good but as a byproduct also looks good. She listens to mainstream stuff, her age group seems to have a fascination with One Direction, but mainly pop/top 40 style music at the moment but tends to change quickly.
Should be somewhat rugged to hold up to the use of a teenager, 3.5mm plug of course. Easy to drive from an ipod/iphone, she may enjoy an amp but may not want to deal with charging/carrying another piece at the moment.
She likes my MS1's and AKG K240 Monitors, but I don't think she has the personality to rock those in public.
Budget up to around $200