If you slow the video down to .25X you can actually see her casting the spells.
Maybe She Really Is Magic: Magician’s ‘Quick Change’ Act Stumps Penn & Teller

This is a segment from Penn & Teller: Fool Us (season 7, episode 8) starring French magician Léa Kyle and her incredible quick change act, in which she repeatedly changes outfits in an instant. Even Penn & Teller aren’t sure how she performed all of them. And, perhaps even more impressive, I’M not sure how she performed some of them. “Oh, because you’re the authority on magic?” I don’t know, have you seen, THIS? “I swear if it’s the detachable thumb trick again.” What, you’d be totally mystified?! One thing’s for certain though, and that’s I wish my girlfriend could get changed so quickly. Haha, isn’t that right hon– *ducks under thrown shoe*