<P> On October 29, 2009, she was one of the This is It dancers who appeared on The Ellen DeGeneres Show to fulfill host Ellen DeGeneres' birthday wish . </P> <P> She appeared in all first - season episodes of Undercovers . She plays a character named Lizzy Gilliam, who is the sister of the female lead and who is unaware of her family's involvement in Central Intelligence Agency activities . Originally, Jessica Parker Kennedy was cast in the role, but Cox replaced her in June 2010 before the first episode of the first season was aired in September 2010 . Her character is described as "Boy crazy". Cox says that Lizzy's character, which spends much of her onscreen time running the family catering business, embodied much of her own true character and described the character as follows: "Lizzy's a good character; very light - hearted, very fun loving, she's got a good heart and an interesting past and she's trying to deal with it". </P> <P> In 2016, Cox appeared in the Modern Family episode "The Cover - Up". On August 23, 2016, Cox joined Chicago Med in a recurring role . She portrays Tiana in the seventh season of Once Upon a Time . In August 2017, Cox was promoted to a series regular on the series . </P> <Table> <Tr> <Th> Year </Th> <Th> Title </Th> <Th> Role </Th> <Th> Notes </Th> </Tr> <Tr> <Td> </Td> <Td> I Kissed a Vampire </Td> <Td> Nikki No </Td> <Td> </Td> </Tr> <Tr> <Td> 2011 </Td> <Td> Crazy, Stupid, Love . </Td> <Td> Hip Hairdresser AKA Tiffany </Td> <Td> </Td> </Tr> <Tr> <Td> 2012 </Td> <Td> Battlefield America </Td> <Td> Sarah Miller </Td> <Td> </Td> </Tr> <Tr> <Td> 2013 </Td> <Td> The Exchange </Td> <Td> Lisa </Td> <Td> Short </Td> </Tr> <Tr> <Td> 2013 </Td> <Td> After Dark </Td> <Td> Bree </Td> <Td> </Td> </Tr> <Tr> <Td> 2015 </Td> <Td> The Squeeze </Td> <Td> Lana </Td> <Td> </Td> </Tr> </Table>

Who plays tiana in once upon a time
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