One year after Michelle Trachtenberg died at 39, her 'Buffy the Vampire Slayer' costar Sarah Michelle Gellar and 'Gossip Girl' costar Taylor Momsen shared touching messages. “It’s weird how the body clock remembers,” Taylor wrote in a Feb. 26 Instagram post. “Last night I was sitting in my hotel room alone in São Paulo, I didn’t know what the date was (they all blend together on tour) and I was hit with an overwhelming sadness over Michelle…then I wake up and realize it’s been a year without her. Life is hard.” Meanwhile, Sarah reminisced on how “lucky” she was to have had “30 years of memories” with her late ‘Buffy the Vampire Slayer’ costar. “From our first day on set together, to less than a year later, when you were already taller than me,” Sarah penned in her own Feb. 26 Instagram post, alongside old photos of herself and Michelle. “ I watched you become a star with ‘Harriet’. You were great to my kids. Countless kids b-days you attended even though I’m sure you had somewhere cool...