Buffy the Vampire Slayer is my favorite TV show of all time. While I have often seen Dawn, Buffy’s little sister, referred to as one of the worst TV characters—sometimes even the worst—she was one of my absolute favorites from the series. The news of actor Michelle Trachtenberg’s passing still doesn’t seem real, and has made me reflect on both her career and her role as Buffy’s little sister, who was actually so much more than that.

As a teenager, I was positively smitten with Michelle Trachtenberg. That never entirely went away. She has always been one of those actors for whom I will watch whatever the movie is solely because I see that she’s in it. It is a surreal feeling to know that’s happened for the last time. I’ve been grateful, as new generations and audiences discover Buffy, to...