Delhi Development Authority [DDA] — dda rohini scheme 1981/ priority no 16931/application no 231542

My mother had booked the plot in rohini 1981 plot scheme, priority no 16931. We had transferred the flat from my mother to my father name after my mother death. But after my father sudden death, my middle sister somehow managed to transfer the plot on her name alone. We are 6 siblings and we had also placed the required documents in dda. Then how could dda transfer the plot to my sister name without our consent. They must asked for our approval for the transfer of plot.