Buffy: Buffy was Dawn's older sister (Image: The WB) READ MORE Actress Trachtenberg was cast to play the 14-year-old character back in 2000 and she starred in a total of 66 episodes. The star is now 35 years old and she was born in October 1985 - this means she would have been about 15 when she played Dawn. Her character was portrayed as much younger than her actual age, as she was seen as immature and clumsy. Buffy was known to have treated her like a child and would often moan when it came to babysitting her. However, their relationship changed when Buffy discovered Dawn's real identity and she was determined to protect her sister.