The actress, who is rocker Phil Collins' daughter, studied fencing with professionals before shooting a pivotal fighting scene with co-star Armie Hammer.
She tells Britain's Empire magazine, "We were so proud when we finished the fight scene because the way (director) Tarsem (Singh) shot it proves it was really us (doing the stunts)."
And Collins insists the training has really paid off for her: "I think I could defend myself with a sword now, too. I could beat Armie. He's taller than me and he's really strong, plus he had the more formal training. But I got trained by dwarf bandits, so obviously I'd win... They're robbers, a band of professional thieves."
And Hammer adds, "That was my favourite bit (of the film). I can (now) fight with a sword! How many people can say that?"