Well, being a teen myself I understand this. I am 14 however, feel much, much older in the mind. If you can imagine sometimes, when you feel more mature especially as a teen, you tend to want to spend time with older people (the ones you feel are your true peers). It is important for a sense of breaking away and succeeding in independence.With people your own age or younger people, it is almost a burdon, like a younger brother or sister who does not have the maturity or problems/interests as you. I would suggest that you ask her is there any opportunites where she would like to mix with older people, i.e after school clubs and such. Alternatively, see how it goes for a while at school. Try to find chances for her to mix with older people aswell as people her own age, then hopefully she can see the benefits and also downsides to both. Feeling more mature than your age is one of those great draw backs in teenage life, for you cannot always enjoy yourself or truly express your mind to your friends. Good luck.