At age 14 a girl could be taking pills to prevent pregnancy, to enlarge feminine features, to clear acne, or to reduce blood during periods. Pills have side effects and their use should be well guided. There should therefore be expert consultation for such an incidence.
Well when I went to the doctor I asked her about cures for acne and one of the solutions was birth control pills. Other reasons could be to lighten period, reduce PMS, no cramps, and of course birth control.
I took them just for acne, it helps, and maybe she just wants to be on it for when she is ready to have sex, it could be anything. she also might just want to be on it b/c people thinks its cool, it just depends on the person