Final answer:
Old Granny's potential grudge against Rukmani could be due to neglect of her needs, which frequently happens in old age when individuals become dependent on others for care.
Step-by-step explanation:
Rukmani might have cause to bear a grudge against Old Granny due to neglect of her needs. The text suggests a situation where an elderly person, possibly resembling Old Granny, is left alone and uncared for in their times of need. As people grow old, they may become frail and depend heavily on others for care. It is at this stage that neglect can be a significant issue.
The provided passages mention the hardships of old age, including dependency on care and loneliness, which might foster a grudge if Old Granny felt that Rukmani had neglected her. However, the question states that Rukmani is happy that Old Granny bears no grudge, indicating that neglect might not have occurred in their specific relationship.