Sasha Alexander (born May 17, 1973)  is an American actress. She is best known for her roles as Helene Runyon on Showtime's Shameless, Maura Isles on TNT's Rizzoli and Isles, Jessica in Love Happens (2009), Catherine in He's Just Not That Into You (2009), Lucy in Yes Man (2008), Melissa in Mission Impossible III (2006), Special Agent Kate Todd on the first two seasons of NCIS, Dr. Jackie Collette on CBS's Presidio Med, Jesse Presser on ABC's Wasteland, and Gretchen Witter on Dawson's Creek.