My father and my uncle own a joint DDA flat in Delhi. My father expired last year. Now my father's s

My father and my uncle own a joint DDA flat in Delhi. My father expired last year. Now my father's sister says she has a Notarised Power of Attorney of the whole flat and she says she has the ownership of the complete flat .  I have got the Relinquishment Deed executed in my name for the half undivided share of my father at the local SDM office in Delhi. Now i and my uncle want to sell the flat and divide the property equally. My uncle and I have no dispute and issues.  My aunt is threatening us with a Police complaint if we sell the flat.  How can we get a solution to this legal issue. We have the Conveyance Deed of DDA having my father's name and my Uncle's name. We and my Uncle have no dispute and we want  to sell the flat soon . Please advise on the legal issue