Hello , during puberty as she would have her first menses , the hormones and the pain because of menses , will release more adrenaline and cortisol like hormones in the blood stream , which will make the heart beat stronger and faster resulting in a palpitation like feeling . She need to be reassured and if required analgesic like locally warm compress on lower abdomen or tab mefenemic acid according to her weight if pain accompanies palpitation. However if it persists more than 3 - 6 months till things normalise , a consult with the doctor is suggested particularly I d there is any breathlessness associated . Regards Dr Priyank Mody