Dawn Summers on 'Buffy the Vampire Slayer' was magical energy turned human. Michelle Trachtenberg made her everyone's kid sister.

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.

Actress Michelle Trachtenberg, who rose to fame as a child star in the 1990s and 2000s, has died aged 39. Police in Manhattan said they responded to an emergency call on Wednesday morning and found Trachtenberg "unconscious and unresponsive". She was pronounced dead at the scene.