From
http://gameofthrones.wikia.com/wiki/Talisa:
Behind the scenes
Originally, Chaplin was only announced as playing 'Jeyne', leading to fan speculation that she would be playing either Jeyne Westerling, a noble girl of the Westerlands, or Jeyne Poole, a friend and companion of Sansa Stark's who accompanies her to King's Landing.[2] It was later announced to be Jeyne Westerling.[3] However Chaplin's character introduces herself as Talisa when she first appears. She goes on to say that she is from the Free City of Volantis, while Jeyne Westerling is actually a member of House Westerling, minor nobles from the Westerlands sworn to House Lannister; however, Jeyne's great grandmother was indeed from the east.