Michelle Trachtenberg, the actress who rose to fame as a child star with films like “Harriet the Spy” and went on to have memorable roles on TV shows including “Gossip Girl,” has died, according to an NYPD source.

When the series shifted from the WB to UPN for its sixth season, fans were treated to one of its most innovative episodes: the musical Once More With Feeling. Most prominently for Trachtenberg, whose ballet talents were showcased that week, she opens the episode’s coda, “Where Do We Go From Here?,” singing the opening title line a cappella.

Michelle Trachtenberg, a former child star who appeared in the 1996 “Harriet the Spy” hit movie and went on to co-star in two buzzy millennial-era TV shows — “Buffy the Vampire Slayer” and “Gossip Girl” — has died.