The narrator's grandmother is isolated in the city for a number of reasons. For one thing, she's a traditional Indian woman from a rural background who feels completely out of step with modern society. Her growing estrangement from both her society and her grandson can be seen in her disapproval of what the young man is being taught at school. There's no God or religion on the curriculum; what's more, the young man is being taught music, which to his grandmother is something one normally associates with courtesans and other disreputable characters.
The grandmother's response to the modern world, a world she neither appreciates nor understands, is to retreat from it. She spends her whole day absorbed in prayer and feeding sparrows. This has the effect of weakening her emotional attachment to her grandson. When she comes to the railway station to see him off to college, it's noticeable that she shows no real emotion. Instead, she spends most of the time engrossed in her prayers and saying rosaries.