Need advice on financial security and property rights

Situation: My cousin sister (Hindu) married for 30 years has two sons. She was working for Govt organisation but on the insistence of husband left the job & financially dependent on BIL. Brother-in-law started business, under 3 different companies. Proprietorship : : Company x : Owner is my sister ComPany Y : Owners are my BIL & Nephew Company Z: Owner is BIL Income from these 3 companies : 50:30:20 The total income incurred against all the three companies have been drawn by BIL (TELLING my sister that it is going to be used for procurement of immovable properties). recently, he sold couple of properties but money is kept with him, has not disclosed the whereabouts of money arising out of sale of properties. It is gathered with evidence that my BIL has extra marital affair and does visit his own house only for few hours in a day leading to mental torture to my sister. He does not give sufficient money for the maintenance of house. Advice on financial security & her property rights.