For the most part, Anne's quite distant from her sister. Although she greatly respects Margot, Anne isn't emotionally close to her. There's something almost too perfect about Margot that prevents Anne from developing any real sisterly feelings toward her. Yet it's emotions that place an additional strain on their less-than-ideal sisterly relationship. Anne becomes consumed with jealousy over Margot's obvious affection for Peter Van Daan. Anne has feelings for Peter and doesn't want to share him with anyone else, least of all her big sister. But in the claustrophobic confines of the secret annex, it becomes necessary for the two sisters to sort out any problems that may arise between them; otherwise, life will become even more unbearable, both for the sisters and everyone else.
So in an exchange of letters in late March 1944, the sisters reveal their thoughts to each other. Margot tries to reassure Anne that she has no need to be jealous. Anne, in reply, expresses her thanks for Margot's kindness and understanding in this delicate matter. Yet at the same time, it's notable that she goes on to say that she's still unhappy about the situation and always will be. Anne's letter encapsulates her relationship with Margot: she respects and admires her big sister, but there's not much in the way of warmth between them.