My niece asking to vacate her father's room

1. I am 70 and living in my own flat in Mumbai, since year 2000.
2. I was living with my elder brother (elder to me by 15 years) in his rented house in a chawl since 1945.
3. In 1956 my elder brother moved to a different city due to his job and later in 1978 he died. His wife died soon after that. He has got 1 daughter, who is 50 today.
4. In 1956, because I did not have a home in Mumbai, instead of surrendering the rented house, my brother kept the rented room for me and since then this room is in my possession, even today. I have been paying the rent and the electricity bill, though both these documents are on my elder brother’s name.
5. Now my elder brother’s daughter is asking me to vacate the rented room. I told her to pay me something and I will vacate the room, but, she says,” My father did a favour to you by NOT surrendering the room when you were in trouble. Therefore, I will not pay you anything, because, you stayed in my father’s house for so many years, and therefore you paid the rent and electricity. Moreover, nothing comes free in this world. Uncle, in fact, when you got your own flat in 2000, you should have given my father’s flat back to me without asking”.
6. Today, I received a letter from my brother’s daughter. In letter, she said,” Uncle, I have surrendered the room to the owner of the Chawl and told him that he will get his room vacated after 30 days. Therefore, uncle, you must vacate the room in next 30 days.”
7. What should I do today? What will happen if I do not vacate the room in next 30 days?   

Thanks for help