The 22-year-old donned a blonde wig, thigh high boots and mini skirt to perfectly replicate prostitute, Vivian Ward, from the 1990 mega hit flick.
Emma - who was joined by her American Horror Story boyfriend, Evan Peters - wore the revealing outfit to attend Hollywood insider Mike Meldman's annual Halloween party in Los Angeles on Friday.
The We're the Millers actress was the spitting image of Julia who was just 24 years old when she was nominated for an Oscar for the role alongside Richard Gere.
Despite the remarkable similarities Emma - whose dad is actor Julia's brother Eric Roberts - has always insisted on making her own way in Hollywood.
"I'm just doing my own thing," she has said in the past. "I don't really compare it to what my aunt does, but I do admire her and love all her movies."