Ms Duff, best known for her role in Taggart, won the best female performance prize at the Critics Awards for Theatre in Scotland (Cats) yesterday for one-act monologue Ciara.
The production of Crime and Punishment won four awards, with director Dominic Hill winning his fourth Cats award.
Ms Duff won the same award last year, for her interpretation of convicted husband-killer Fay Black in Iron. In Ciara she played the daughter of a recently deceased gangster in a play written by David Harrower, which also won the Best New Play award.
Crime and Punishment - a Citizens Theatre, Liverpool Everyman and Playhouse, and Royal Lyceum Theatre, Edinburgh, co-production - was described by judges as a "consummate piece of theatre," and won four awards including Best Production.
Adam Best was named Best Actor for his "epic performance" as Raskolnikov, and the "dazzling achievement" of the 10-strong cast earned them the Best Ensemble award.
The Imaginate Festival, which has made theatre for young people for 25 years, was presented with the Cats Whiskers award.