Answer by taking a quote from the following article:

Olivia Dunham is a fictional character and the main protagonist from the science fiction television series Fringe, which aired on the Fox Broadcasting Company in the United States from 2008 to 2013. The character was created by series' co-creator J. J. Abrams, and is portrayed by actress Anna Torv. Olivia is the series' protagonist, and was introduced as an FBI Special Agent, working for a multi-agency task force of the U.S. Department of Homeland Security called the Fringe Division, dealing with supernatural events that are linked to experimental occurrences. Having grown up with an abusive stepfather, Olivia struggles with the unexpected changes in her life, following her encounter with mentally unstable scientist Walter Bishop, and his son and an eventual love interest for her, Peter Bishop.

Comparing Olivia to Fauxlivia, Torv felt that the two had many different characteristics. Anna Torv described them as "remarkably alike. They have subtle differences, but they're both fighting for their causes. I think each of them sees things in the other they'd like to have. I think Olivia would like to not feel everything is her responsibility. She'd like to go home and let someone else shoulder that burden of saving the world for a few minutes."  Torv and Akiva Goldsman discussed various ways to differentiate the two depictions of Olivia; ultimately two different physical demeanors were created. Torv wanted to make the new character "completely different", but she and Goldsman recognized that the two share some major similarities, as they both are in the same profession and are "fundamentally, genetically really the same person." According to Torv, Fauxlivia holds herself differently and has "a different silhouette. She's got a little firefighter, a little military in her." Torv further explained, "Olivia wants to be the best, but [Fauxlivia] just wants to win;" "There's just a front-footedness I think to [her], simply because she just doesn't carry the weight of the world on her shoulders like Olivia does. Olivia's mum died when she was really little, and [Fauxlivia]'s mum is still around. There's lots of little, subtle differences."  The producers discussed cutting her hair, but ultimately decided on the auburn hair color to differentiate her. They also made her "a little bit more playful". Pinkner describes shooting the Fauxlivia scenes in the DVD audio commentary: "When [Torv] first showed up on set in this different guise, she had really embodied this other character in a very playful and sexy way. She turned a lot of heads." Goldsman remarked that Torv's depiction of Fauxlivia was actually much closer to the actress' real personality than her performance as Olivia. The producers were so pleased with her Fauxlivia depiction that they thought "it really opened up a bunch of possibilities ... it went from 'let's see if this experiment works' to 'how can we get more of this?'"

what else is different about fauxlivia?
" "There's just a front-footedness I think to [her], simply because she just doesn't carry the weight of the world on her shoulders like Olivia