Concept:
In blood relation problems, identify each relationship step-by-step and connect them logically.
The term {maternal grandmother} refers to the mother of the person's mother.
Step 1:Identify the nephew.
The man mentions his nephew.
A nephew is the son of one's brother or sister.
Step 2:Find the maternal grandmother of the nephew.
Maternal grandmother = mother of the nephew's mother.
If the nephew is the son of the man's sister, then the nephew's mother is the man's sister.
Step 3:Identify the lady in the photograph.
The lady is the maternal grandmother of the nephew, which means she is the mother of the man's sister.
Step 4:Relate the lady to the man's sister.
Since the lady is the mother of the man's sister, the relationship is:
\[
\text{Lady} = \text{Mother of the man's sister}
\]
Thus, the lady is the Mother of the man's sister.