Second marriage when person was minor at the time of first marriage

Doubt about child marriage happend in 1979 at scheduled caste village : my relative sister age 47 belong to schedule caste family living at village,on year 1979 at her age of 13 she was forcely married to her relative person ,he was arrogant and drug addict and done adultry, after six month she approach her relatives and told what arrogant she faced so they approach panchayat elders according to their valid customs they dissolute their child marriage with both mutual understanding.(in that scheduled caste village at that period no one go to court and police station they only appeal panchayat and elders in village) after ten years at age of 24 she married another good person with permission of panchayat elders. please tell her second marriage is valid or not ?.