When Peter first moves into the secret annex, Anne dislikes him from the start. Though she was looking forward to his arrival as another form of company in their quiet home, the reality of the shy, awkward boy is incredibly disagreeable to her. She describes him as lazy and tedious, noting in her second entry about him:
He's an obnoxious boy who lies around on his bed all day, only rousing himself to do a little carpentry work before returning to his nap. What a dope!
As they continue to live together, Anne's frustration with Peter does not change. She tries to tutor him in English, but becomes infuriated by the ridiculous mistakes he makes in his lessons, and she is easily irritated when the grown-ups praise his modesty and mild manners, traits that Anne notably lacks. When she is asked by the Van Daans whether she could ever learn to love Peter like a brother, as he loves her like a sister, she reacts with barely contained disgust.
However, even early on, there are small moments of connection between Anne and Peter. They both enjoy dressing up, and one evening they put on costumes to entertain the other inhabitants of the Annex. Perhaps this is the reason that Anne takes it into her head in the beginning of 1944 to try to become friends with Peter. Her loneliness has become so unbearable that she has to find someone to talk to. She claims she selects Peter because he is the only other young person besides her sister, not out of any sentimental feeling for him:
You mustn't think I'm in love with Peter, because I'm not. If the van Daans had a daughter instead of a son, I'd have tried to make friends with her.
She sits in his room and tries to talk to him, aware of the awkwardness he feels but persisting nevertheless and assuring him that he'll grow more comfortable talking to her over time, even though she is a girl.
Her prediction turns out to be right. Peter is as starved for a sympathetic friend as Anne is and they soon become comfortable talking with each other about anything and everything. They complain to each other about the other inhabitants of the annex and share their thoughts on the war and their lives after they are out of hiding. They study together and become each other's closest confidantes in the annex, often spending time together in Peter's room away from the prying eyes of their families. However, Anne insists that she still harbors no romantic feelings for him:
Don't think I'm in love, because I'm not, but I do have the feeling that something beautiful is going to develop between Peter and me, a kind of friendship and a feeling of trust. I go see him whenever I get the chance, and it's not the way it used to be, when he didn't know what to make of me. On the contrary, he's still talking away as I'm heading out the door.
Yet despite her insistence, her growing feelings for him cannot be denied. She becomes despondent when she doesn't speak to Peter all day and confesses a desire for him to hold her. Part of this may be the fact that the line between Peter van Daan and Peter Schiff, Anne's schoolyard crush, is becoming incredibly blurry. Anne admits that the two have merged into one Peter in her mind that she longs for hopelessly.
Though Anne finally realizes her attraction to Peter, his feelings remain unclear. Sometimes Anne thinks he might feel the same way and at other times she feels he is distant and has more interest in Margo than in her. Eventually, he reveals himself in his own shy, quiet way. Anne and Peter begin sitting with their arms around each other or gently holding each other. The physical relationship develops and they begin to kiss each other when they have time alone in Peter's room. Anne believes that they are in love with each other and relishes in her first experience of romance.
However, the shine soon wears off their relationship. Though they remain close friends, Anne and Peter begin to distance from each other, realizing that they are not as compatible as lovers as they thought.