What is the correct way to write a WILL?

My parents are planning to write a registered WILL. They have four daughters and no sons. All daughters have been married for many years and have children. I am the youngest daughter, but my husband passed away, so I am staying with my parents. I don’t have any children. My mother owns a house in her name. My father is alive, but he is mentally weak. She wants to write a registered WILL for this property without informing my three sisters. She wants to mention that all four daughters are equal beneficiaries, but my father should have the right to stay/use the house for his lifetime (in Telugu, the word is “Anyakrantham”). If she writes the WILL like this, what problems might we face in the future during execution? Will my sisters respect my father, since they don’t need to ask him about the property (because my mother already wrote the WILL)? Another doubt is about property sharing disputes between sisters. All will get equal rights, but dividing the house part-wise is not suitable. Please suggest the correct way to write the WILL.