Mrs. van Daan (whose real name is Auguste van Pels) is Mr. van Daan’s wife and Peter’s mother. Anne initially describes Mrs. van Daan, whom she sometimes refers to as Petronella van Daan, as a friendly, amusing woman. For example, Anne finds it funny that Mrs. van Daan has insisted on bringing her chamber pot to the annex.

Ultimately, however, Anne finds Mrs. van Daan, like her husband, difficult to live with. She constantly bickers with Mr. van Daan and fights with Anne’s mother about household issues. She is not happy that the families are using her china and not the Franks’, and she is reluctant to share her family’s linens with the rest of the annex. Mrs. van Daan also repeatedly irritates Anne by scolding her and lecturing her as if she were her own daughter. For example, Mrs. van Daan becomes enraged when Anne does not eat enough vegetables. Anne records a memorable dinner in which Mrs. van Daan says that Anne “should have been at our house, where children were brought up the way they should be. I don’t call this a proper upbringing. Anne is terribly spoiled. I’d never allow that. If Anne were my daughter…” However, while Anne is angered by Mrs. van Daan, she does not seem to make much of an effort to understand why she and the rest of the adults are acting the way they are, a reminder that Anne is still a young girl and not yet wholly emotionally mature.