does she have any headache?have u got her checked for migraine
which can sometimes start after puberty
.r her symtoms related to menses say,1wk before periods?if yes it cud b just premenstrual
syndrome. Also plz look into her personal life for any emotional changes as this is the age children fall into infatuations n bad company which may affect their psyche.
b assured it will pass away as she grows.
Hope i cud help.