Sarah Michelle Gellar, more 'Buffy' cast pay tribute to Michelle Trachtenburg

Sarah Michelle Gellar is mourning the loss of her Buffy the Vampire Slayer co-star and on-screen younger sister Michelle Trachtenberg.

A day after news broke of Trachtenberg’s passing at age 39, Gellar, 47, took to Instagram with a tribute, sharing a mix of personal photos and Buffy memories.

"Michelle, listen to me. Listen. I love you. I will always love you," she wrote, quoting an emotional line from their iconic show. "The hardest thing in this world is to live in it. I will be brave. I will live… for you."

Gellar wasn’t the only Buffy alum to honour Trachtenberg’s legacy.

James Marsters, who played Spike on the hit series, remembered her as "fiercely intelligent, howlingly funny, and a very talented person," adding that she "died much too young."

Alyson Hannigan also shared her grief, writing, "She brought a loving energy to the set of Buffy," while David Boreanaz called the news "so very sad… horrible."

Emma Caulfield Ford, who played Anya, reflected on the loss of their on-screen “little sister,” writing, "I'm so sorry your bright light died so young."

Trachtenberg, best known for her roles in Buffy, Harriet the Spy, and Gossip Girl, passed away on February 26. 

While her cause of death has not been officially disclosed, reports indicate she had recently undergone a liver transplant.