Widow propery rights

I am Tharun V Bhatt from Bengaluru, I have a sister by name Devika who lives in Coorg and she recently lost her husband in an accident. She is now left with two minor kids with no source of income. Devika's husband has a property which is jointly registered along with his mother. Now, Devika's mother in law is trying to get the Record of Rights transferred to her name only, without including my sister's name. Is this legal? Ideally, what belongs to husband will have to be transferred to wife right? This property was purchased and was not an inherited property. Does my sister not have a legal claim to get her name on the property in place of her husband? Devika's mother in law is a well to do lady with separate property and also gets widow pension. She has no dependents either, on the contrary, my sister is a widow with two minor dependent kids with no source of income. What should my sister do to get her name included in the property inplace of her husband? Please advise. This is crucial for my sister's survival. She could be thrown out of the house if the property is registered in her mother in law's name only.