Is daughter-in-law bound to care for MIL even though she has harassed the DIL multiple times in past

I am an Indian working female (25). My mother is almost 60 and brother is a special child (30). I lost my father 4 years back. My father's parents kicked my parents and my brother out of their home 28 years back (1992). After grandfather dies in 2000, grandmom lives alone for couple of years. In 2005 she looses all her money(about 50L) and property to a fraud and she is now living on minimal finance. 2008 she breaks her leg and since no one cares for her, my father took her back in. She starts harassing my mother and me mentally and emotionally. So my father took her with him to a different town where he works. We had to live in different towns due to her. After my father died in 2017, relatives are trying to push grandmom on us even though we are struggling to live ourselves (financially and emotionally). Note: We never inherited any property either from grandparents or from father. We never utilised any money whatsoever in this entire duration. My grandmother has a daughter who has benefitted entirely financially from them but now refuses to care for her. Are we legally bound to care for a woman who was never family to us? Is there any law to protect people like us from harassing relatives?