Anne admits in her diary that she is always being compared to Margot (although we see very little of Margot ourselves). Margot is always seen as the more mature, passive, and level-headed of the two sisters. She’s also the pretty one, the smart one, and the one who is well behaved. It seems that in the minds of all the Secret Annex folks, for better or for worse, Anne is the complete opposite. Anne isn’t remotely passive, she has opinions about everything, gets into arguments, is a pest, and is also funny and outgoing. Because Anne is compared to Margot, who sounds like she’s the ideal 1940s daughter, Anne is often treated like an immature child and not very well respected.
Many of Anne’s positive personal characteristics are highlighted simply because Peter lacks them. For example, we learn that Anne cares about active personal growth because she’s disappointed that Peter is so lazy about it and doesn’t invest in personal improvement because it isn’t easy. We also learn that Anne isn’t the atheist that she sometimes seems; she is mad that Peter is not religious and even disrespectful of religion in general.