Who was Harriet the spy caught spying on in the dumbwaiter?

In the book "Harriet the Spy" by Louise Fitzhugh, Harriet is caught spying on her classmates, particularly on her friend, Janie, while hiding in a dumbwaiter. This incident leads to significant repercussions in her relationships and serves as a turning point in the story, highlighting the themes of friendship and betrayal. Harriet's observations are candid and often unfiltered, which ultimately complicates her interactions with those around her.