Pointing out to 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 that girl?

Mother

Pointing out to 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 that girl?

According to the given data,

Girls's father's only son— Girl's brother. Daughter in law of girl’s grandmother can be their mother.