The changing relationship between the author and his grandmother in the story "Portrait of a Lady" by Khushwant Singh is a central theme. The story follows the author's memories of his grandmother, starting from his childhood until she passes away.

Initially, the author remembers his grandmother as a strict and unapproachable figure. He describes her as a "formidable woman" who had a "sharp tongue." However, as the story progresses, the author's relationship with his grandmother changes, and he starts to see her in a different light.

The author's grandmother passes away, and he is left with a feeling of regret that he did not get to know her better. He realizes that his grandmother was not just a strict and unapproachable figure, but she was also a woman who had lived a long and eventful life. He wishes that he had taken the time to listen to her stories and learn from her experiences.

Throughout the story, the author's feelings for his grandmother change from fear and intimidation to regret and longing. His grandmother's feelings towards him, however, are not explicitly stated. It is clear that she loves her grandson and wants what is best for him, but it is uncertain whether her feelings towards him change throughout the story.

Overall, the changing relationship between the author and his grandmother in "Portrait of a Lady" is a poignant reminder of the importance of taking the time to get to know the people we love before it is too late.

Relationship between author and his grandmother changed when they shifted to city because:-
1)Now author started to go to school by bus, his grandmother can't drop him.
2)As author has got admission in a English school so he was taught science and English in which his grandmother was not able to help.
3)The thing which most disturbed the grandmother is that when she came know that author was also taught music in school.

After all this incidents also their feelings for each other didn't change.