Can my father’s brother's wife make a valid gift deed?

The property document is in my father’s father's name (i.e., my grandfather). My father has 3 brothers, and all of them have passed away. There is no will executed by my grandfather, and no partition has been done till date. My father's brother's wife has made a gift deed in her only daughter's name. Is it valid? Some of my cousin brothers are not coming forward for partition. What should be done in this case? Is it legally valid for cousins who are interested to give a no-objection letter for my father's 1/4th share?