Los Angeles, California - Buffy the Vampire Slayer star Sarah Michelle Gellar honored Michelle Trachtenberg with an emotional message.

The 47-year-old actor shared a heartbreaking tribute on Instagram in honor of the late actor who played her little sister, Dawn Summers, on the supernatural TV drama.

Gellar posted images of herself with Trachtenberg throughout the years, including a photo of the Harriet the Spy actor holding one of Gellar's children and another of the co-stars posing with the late Shannen Doherty.

The I Know What You Did Last Summer actor captioned the carousel of snaps, "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."

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Buffy fans may remember the poignant quote from the popular series, as it was Gellar's character's last line to her sister during the season 5 finale.

Trachtenberg, who was also known for roles in EuroTrip, Gossip Girl, and Ice Princess, was pronounced dead at the age of 39 after being found "unconscious and unresponsive" in her New York City apartment.