Why did petra's parents argue about the letter in chasing vermeer?

In "Chasing Vermeer," Petra's parents argue about the letter because they disagree on its significance and the implications it has for their family. Petra's father is concerned about the potential consequences of the letter, while her mother is more focused on its mysterious and intriguing nature. This disagreement reflects their differing perspectives on the importance of the past and how it affects their present, ultimately influencing Petra's own curiOSity and quest to uncover the truth behind the letter.