An Overheard Conversation

Even after all these centuries, Anna Sackville-Bagg is still haunted by the one memory she had when she was still mortal. They were harmless bad dreams, but with the sight of Tony being covered in blood, the memories manifest into something worse. Luckily, it turns out that her family wasn't as cold blooded as she originally thought.
(This has a mix of traits from the movie and the book, as well as a ton of headcanons and canon deviance because trauma is fun and its a shame children books don't have much of it.)