Blake Lively and Alyson Hannigan are among the former "Gossip Girl" and "Buffy" actors mourning the death of their one-time co-star, Michelle Trachtenberg.

Blake Lively broke her social media silence on Wednesday to pay tribute to her late “Gossip Girl” co-star Michelle Trachtenberg, who died Wednesday morning at 39. In an Instagram Story, Lively remembered Trachtenberg as a “fiercly loyal” and “kind person, through and through.”

On Feb. 26, news broke that Michelle Trachtenberg, the actress who played Georgina Sparks in ‘Gossip Girl,’ passed away. Several actors from the series have paid tributes to her on social media.