Sarah Michelle Gellar Shares Heartbreaking Tribute To 'Buffy' Costar After Her Tragic Death

Buffy the Vampire Slayer and Gossip Girl fans were left reeling today at the sudden loss of Michelle Trachtenberg.

Also well-known for her roles in Harriet the Spy, 17 Again, and Ice Princess, Trachtenberg was a Millennial icon, but in recent years, she had severe struggles with her health, including the need for a liver transplant.

Michelle Trachtenberg was found dead in her apartment on Wednesday morning. No suspicious activity was detected, and it's believed that she died for reasons related to her health and liver transplant.

Since the news started to circulate, celebrities have been expressing their grief at the passing of their coworker and friend, but the tribute made by Sarah Michelle Gellar was especially touching.

Gellar, who starred as Buffy and welcomed Trachtenberg as her younger sister, Dawn, in season five of the show, always openly referred to her as her little sister and friend.

In Gellar's tribute on Instagram, she used a popular quote from the end of season five when Buffy sacrifices herself for Dawn:

“Michelle, 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… for you."

Fans were moved by Gellar's tribute and heartbroken to hear of the loss of Trachtenberg.

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

@sarahmgellar/Instagram

With Gellar leading the way, other Buffy cast members came forward with tributes.

"Spike" from the show, James Marsters, wrote:

"My heart is heavy today. We have lost a beautiful soul."

"Michelle was fiercely intelligent, howlingly funny and a very talented person."

"She died much too young, and leaves behind scores of people who knew and loved her."

"My heart goes out to her family, who are good people and are suffering the greatest loss anyone could bear. I hope everyone can give them space to heal in this most difficult time. Godspeed Michelle. You are missed."

"Willow Rosenberg" from the show, Alyson Hannigan, also wrote:

"I am deeply saddened by the news of Michelle's passing. She brought a loving energy to the set of 'Buffy.' My thoughts are with Michelle's family and friends."

"Angel," David Boreanaz, was one of the first to write in:

"So very sad... horrible news. RIP and prayers to her and her family."

Growing up on the big screen and being the sister many Millennials wanted her to be, Michelle Trachtenberg will be sorely missed by so many.