3 ideas
Bim's grievance ends when she sees her siblings as part of her own substance, not when they apologize or the wrong is corrected. After nearly turning on Baba in rage, she recognizes that the people she resents are woven into her own identity. Refusing to forgive them would therefore mean cutting away part of herself.
In a strained family, both the one who stays behind to care and the one who escapes carry a distorted version of the same past. Tara remembers her flight as guilty abandonment and envies what she imagines was Bim's strength. Bim remembers staying as heroic sacrifice, which hides her own choice to stay and her need for control. Each sibling's account of the past serves to justify the life that sibling chose, so a shared memory never fully matches between the two who hold it.
The past is not left behind; it keeps living inside the present, especially in a house and routine that never change. The novel moves from the adults back through their adolescence and childhood to show that grievances formed early still run adult behavior. Its apparent stillness is really the past repeating itself, and the characters change only when they see that repetition clearly.