What are the rights of senior citizens on self acquired property

My younger brother who was just 33 passed away last December and his wife (he was not living with her for past 3 years) is harassing my parents over their properties. Our both houses which was under my brother name are now transferred to my mom and his wife, as per the law. My dad made her the proprietor of one of the company after his son's demise but the land is under my mom's name. My dad built this company and have been running since 30 years and with good intention of benevolence he took this step but now she is showing her true colors by blocking the account and making decisions against my dad's will. Is their a way that this proprietorship can be made void? Her parents are interfering in our matters and mentally harassing my parents by making undue demands. I am worried about my parents health and security, he already had a by pass surgery 4 years back and is dealing with the grief of irreparable loss of his only son. Can you please advise how to protect my parents from her?