Looking at a portrait a woman said, ‘This man is the son of my uncles’ only brother’. How is the woman related to that portrait?

Sister

Note:

↑ or ↓ ⇒ Upward or downward line shown "generation gap" .

   =    ⇒ Double lines shown "relation b/w Husband & Wife"

   —   ⇒ single line shown "relation between them other than Husband & Wife".

   +   ⇒ Plus sign shown " Male".

   -   ⇒minus sign shown " Female".