Mal's nickname for the young lady we are introduced to in Our Mrs Reynolds as "Saffron". She is a consummate con-artist who gets her kicks not from making the big score but in proving that she's better and smarter than the people she fools. http://www.average-bear.com/firefly/img/YoSafBridge.jpg(approve sites)
The crew narrowly manages to avoid the fate that Saffron leaves them to in Our Mrs Reynolds, but Mal doesn't kill her when he catches up to her—he's just a softie.
We next meet up with Saffron in the episode Trash. Now, her name is "Bridget" and she's married to Mal's old war-buddy Monty. After Mal ruins her honeymoon, she talks him and the rest of the crew into helping her out with a big theft. During the caper, we find out that she was also married to the Alliance commander they're stealing from—under the name Yolanda.
Yolanda... Saffron... Bridget. Yo Saf Bridge. Get it?
Yo Saf Bridge was played by Christina Hendricks(approve sites) (IMDB link). They could not have picked a better woman for the part, Christina pulled off being an amazingly tempting femme fatale and did this with sheer perfection. Double acting within the act of being a natural, and still believable as the pro companion. Best known for her line: "face it hubby, I'm really hot!"