Hollywood is mourning Michelle Trachtenberg — the actor who began her career as a child on The Adventures of Pete & Pete and went on to star on TV shows like Gossip Girl and Buffy the Vampire Slayer and films like Mysterious Skin and Ice Princess.

News of her death broke February 26, and her co-stars have been sharing remembrances on social media since.

Rosie O’Donnell, who starred alongside Trachtenberg in Harriet the Spy, told People she “loved her very much. She struggled the last few years. I wish I could have helped.”

J. Smith-Cameron, who played Harriet’s mother in the film, also issued a statement, saying “I played Mrs. Welch, Harriet’s mother in Harriet the Spy.

Michelle had been on a Nickelodeon show called Adventures of Pete & Pete but this seemed to be her first lead film role. She was so excited.” Smith-Cameron said the two had reconnected over social media once Trachtenberg had become an adult. “She was always very warm toward me,” she wrote. “I feel very shocked and unsettled to hear of her passing.”

Trachtenberg’s TV families shared thoughts and prayers with her family. Alyson Hannigan, who played Willow on Buffy, wrote on Instagram that Trachtenberg “brought a loving energy to the set.”

Kenan Thompson, who’d known Trachtenberg in their Nickelodeon days, urged everyone to “Check on your people.”