<\/p>\n
Michelle Trachtenberg<\/a>, who died this February<\/a>, would have turned 40 on Friday, and her Buffy the Vampire Slayer<\/a><\/em> sister Sarah Michelle Gellar <\/a>marked the somber occasion on Instagram.<\/p>\n \u201cWhen you turned 16, it was hard not to still see you as the little girl I met on All My Children<\/a><\/em>,\u201d Gellar wrote, addressing her late costar. \u201cWhen you turned 21, I had to teach myself to not see you as the little sister anymore. I can\u2019t imagine what 40 would have been like. This I know\u2026 it would be filled with love. Happy birthday @michelletrachtenberg.\u201d<\/p>\n In the final three seasons of Buffy<\/em>, Trachtenberg played Dawn Summers, the younger sister of Gellar\u2019s Buffy Summers. Previously, she played Lily Montgomery on All My Children<\/em> from 1993 to 1996, overlapping with her future Buffy<\/em> sis as Gellar filled the role of Kendall Hart on the daytime drama.<\/p>\n Trachtenberg\u2019s other credits included a lead part in the 1996 film Harriet the Spy<\/a><\/em> and a starring role in the original Gossip Girl<\/a><\/em>.<\/p>\n The actor died on February 26 at age 39, and the New York City Office of the Chief Medical Examiner confirmed to People<\/a><\/em> that the cause of death was complications of diabetes mellitus. Sources told the magazine Trachtenberg had recently undergone a liver transplant and may have suffered complications from that operation.<\/p>\n <\/a> Penn Badgley Shares His Impression of Late \u2018Gossip Girl\u2019 Costar Michelle Trachtenberg<\/p>\n<\/figcaption><\/figure>\n Related<\/p>\n In an Instagram tribute<\/a> at the time, Gellar paraphrased her vampire-slayer character,<\/a> writing, \u201cMichelle, listen to me. Listen. I love you. I will always love you. The hardest thing in this world, is to live in it. I will be brave. I will live\u2026 for you.\u201d<\/p>\n Buffy<\/em> costar Nicholas Brendon<\/a> eulogized Trachtenberg at the time in a now-offline Facebook video, per Entertainment Weekly<\/a>. \u201cWhen we were working together, she was just, like, a beam of light,\u201d he said. \u201cI think it was just the last thing I expected, not that I was expecting anyone to die. But I really am sorry to her family.\u201d<\/p>\n And on Instagram, Buffy<\/em> alum Alyson Hannigan<\/a> said<\/a>, \u201cI am deeply saddened by the news of Michelle\u2019s passing. She brought a loving energy to the set of Buffy<\/em>. My thoughts are with Michelle\u2019s family and friends.\u201d<\/p>\n Read the latest entertainment news on TV Insider<\/a>.<\/p>\n<\/div>\nPenn Badgley Shares His Impression of Late \u2018Gossip Girl\u2019 Costar Michelle Trachtenberg<\/a><\/h3>\n