The case was detected through a video posted online on February 25.
The woman is torturing her mother-in-law (photo taken from the clip)
The woman was identified as Pham Thi Loan, 57, from An Thanh Thuy Commune, Cho Gao District. Loan beat her 88-year-old mother-in-law Vo Thi Dung who is living with her, using a stick.
The clip indicated that a man and a small girl also witnessed the case, but they ignored what was happening.
According to the initial information, Dung is often absent-minded so her daily activities upset her son and daughter-in-law.
The case is under investigation by local police.