Raised in South Carolina as the only daughter amongst four sons, Alexander became interested in acting in grade school. She joined her high school wrestling team largely on a dare but soon became a top wrestler in her 128-pound weight class, all the while continuing to pursue her interest in drama. When a chance meeting with a California scout led to her signing with a manager, she moved to Los Angeles after graduating from high school, and 2009 followed up her turn as a seductive high schooler on "It's Always Sunny in Philadelphia" (FX, 2005-) with back-to-back leading roles in the low-budget, high-impact horror films "Rest Stop" and "The Other Side." That same year she portrayed an adulterous wife on the short-lived series "Watch Over Me" (MyNetwork, 2006-07). The series' quick cancellation proved a blessing in disguise, though, as Alexander landed her biggest role yet on "Kyle XY" playing Jessi, a teenager who discovers she is a genetically modified science experiment. Following in the same fantasy/sci-fi vein, in 2011 she was cast as Asgardian warrior Lady Sif in Kenneth Branagh's well-received "Thor," starring Chris Hemsworth as the title superhero. She branched out yet again with a recurring role as Edie Falco's wild sister-in-law Tunie on "Nurse Jackie," and later landed a guest role as a CIA-analyst-turned-operative in "Covert Affairs" (USA, 2010-14). Since co-starring with Peter Facinelli (with whom she reportedly had a relationship) in the indie romantic comedy "Loosies" (2011), Alexander was cast opposite Arnold Schwarzenegger as a hardened cop in the box-office disappointment "The Last Stand" (2013), and reprised her role of Lady Sif in the 2013 sequel "Thor: The Dark World."