My brother's wife and her family are blaming us of false allegations

we are hindus.my brother married last year in december. since the first step she took in our home,we have been tolerating her medical conditions which we were kept in dark before hand. she suffers from low blood level, PCOS, constant stomach ache etc.also constant taking to her family, taking care of problems going on there, constantly saying she needs to go there, saying hurtful things to our family members, making death threats if thingd dont go according to her.My brother wants to file for a divorce, what should we do and how to proceed from here.