Police said Deepa, 40, the elderly woman's granddaughter, was booked under various sections of IPC, including gain by unlawful means of property to which the person is not legally entitled.
The Kerala State Human Rights Commission has suo motu registered a case and sought report from the district police chief in a month's time.
The elderly woman, identified as Kalyani along with her daughter Devaki, who was also attacked by the woman, has been shifted to hospital, police said.
In the video, the nonagenarian woman is heard wailing as she is thrashed.
One of the woman's neighbours shot the video on his mobile and uploaded it on the social media.
The police filed an FIR after taking cognisance of the video.
A weeping Kalyani is heard in the video saying that she is beaten up every day by her granddaughter and that she has bruises all over.