“Jade coped really well with the terrain and it was a good run. Three seconds is a lot to make up. I never expected us to be that close at the end.”
Etherington and Powell had earlier won silvers in the downhill and slalom, plus a bronze in the super-G.
Now they have overtaken Denise Smith, who won three silvers for Britain in ice sledge speed racing in Innsbruck in 1984.
“We came here just wanting to concentrate on our performance,” Etherington added. “But I told my sisters before I left that I would try really hard to win them a medal. Now we have won four.
“It’s crazy to think that we have done that. I knew we could do it but to have success you have to believe you can do it.”
Their final chance of a medal will be in Sunday’s giant slalom. GB rivals Kelly Gallagher and Charlotte Evans and Millie Knight and Rachael Ferrier will also take part.
Meanwhile, Anna Turney crashed out of the women’s sit-ski event but was able to recover and ski down to the end of the course.
Only two skiers finished both runs in the event and Germany’s Anna Schaffelhuber claimed her fourth gold medal of the competition while Marie Bochet of France won her third gold in the standing division.
Mick Brennan finished eighth in the men’s sit-ski event – his best finish so far, with Canada’s Josh Dueck taking gold.