Competing alongside sister Leonie Gerken Schofield - who failed to qualify for the final - the 22-year-old advanced to the three-part showpiece event as one of the 20 top performers in qualification.
Gerken Schofield posted 73.99 in final one despite a slight mishap after her first jump, which saw her finish ninth as the top 12 performers advanced to final two before the six-person medal showdown.
Speaking to BBC Sport after the final, Gerken Schofield said: "I am struggling to believe it. I had so much fun out there. Eighth place is absolutely incredible.
"It has been a while since I enjoyed skiing but tonight felt incredible. Skiing those bumps, just the feeling - I have no words. I don't know how we (the family) are going to celebrate. It all still feels so surreal.
"My brother (Tom, who missed out on qualifying for Beijing in the men's event) is probably jumping around in the living room with my parents because I have so many messages. I will probably call them and there might be a few tears."
The Brit was down on her score on final two as she recorded a 73.04 and did not make final three, but her eighth-placed finish represents GB's best-ever performance in the moguls at the Winter Olympics.
Anastasia Smirnova of the Russian Olympic Committee managed to sneak into the medals in the third final to take bronze with 77.72, but there was disappointment for Japan's Anri Kawamura, who finished second in final one and third in final two before being forced to settle for fifth in the deciding event. body check tags ::