3 ideas
The narrator openly admits she is inventing what she cannot know and calls her fabrications 'healthy lies,' and a character's refrain asks her to tell a story even if it is a lie. The mechanism is that family history survives only as retold story, so filling the gaps with invention is how the truth of a family gets carried forward. Declaring the invention up front keeps it honest.
The ghost of Lala's grandmother Soledad interrupts Lala's narration to object, correct, and demand her own version. This shows that any family story is argued over by the living teller and the people being told about. The grandmother's ghost cannot rest until her story is told sympathetically, so telling a hated relative's history from inside turns resentment into compassion and completes a debt between generations.
A caramel-striped rebozo whose fringe was left unfinished by its maker passes down to Lala. It stands for family identity as a work each generation keeps knotting rather than a finished inheritance. Like the fringe, the family story has loose threads that the inheritor must tie in her own way, which makes the heir a co-maker of what she inherits.