In decipher jumbled up description type of questions, a round-about description is given in the form of certain small relationships and direct relationship between the persons concerned is to be deciphered.
Pointng out to a lady, a girl said, "She is the daughter-in-law of the grandmother of my father's only son."
How is the lady related to the girl ?
My father's only son -- My brother;
Grandmother of my brother - My grandmother:
Daughter-in-law of my grandmother -- My mother.
So, the lady is girl's mother.