She is played by Lauren Elise.
Jamie is one of the many, many girls Sloane hooks up with.
Jamie meets Sloane at a party. After introducing herself, she drunkenly flirts with Sloane, but she manages to gain Sloane's interest, and the two head to Jamie's house. They then proceed to kiss, take each other's clothes off and sleep together.
Sloane wakes up the following morning, naked with Jamie still asleep, exhausted from their sexual escapade. Sloane quickly takes a drink of whiskey and leaves. She slept with Jamie only as a means of discovering if she'd be a perfect replacmeant.