I am not a medical doctor, so I will not make any comments about your sister's medication.
However, I do think that you need to reconsider the whole situation afresh and definitely take a second opinion from another Child Psychiatrist. I feel that your sister would also benefit by seeing a Psychologist or a School Counsellor. I do not know where you live, so I cannot suggest names or institutions.
Adolescence is a normal period of growth and not a disease condition. Children, at this age, do have self doubts and sometimes, great dissatisfaction with how they look. You need to take your sister to a psychologist, who has handled such problems.
If she is bright, surely she gets some satisfaction in doing some of the school tasks. Try to encourage her to do what she is very good at. Cricket and music sound like very normal interests. What a pity that her classmates talk only of movies and TV serials. Discuss this issue with your
parents and see if it is possible to change schools. But this change will be better done after she has improved her marks and grades. Surely some schools will appreciate their students having an interest in sports and music.
If you are just a few years older than your sister, you are taking on a big responsibility. See if you can get one another adult to join you in this.