Michelle Trachtenberg's death Wednesday left her former co-stars like Blake Lively, Rosie O'Donnell, Melissa Gilbert and Kenan Thompson shocked and saddened.

Louise Fitzhugh’s 1964 children’s novel Harriet the Spy was brought to life in a 1996 movie of the same name. Harriet (Michelle Trachtenberg) is a precocious sixth-grader who’s destined to be a super-sleuth.

Rosie O’Donnell paid tribute to her former co-star, Michelle Trachtenberg, who was found deadin her New York City apartment on Wednesday. “Heartbreaking,” O’Donnell said in a statement to Us Weekly. “I loved her very much.