The New Jersey-born, Brooklyn-raised Keena enrolled at NYC's High School for the Performing Arts and shortly thereafter landed a role in the short "Burning Love" (1993). After playing the lead in the TV biopic "A Promise Kept: The Oksana Bauil Story" (CBS, 1994), she made her feature debut in the ensemble of the hit romance "While You Were Sleeping" (1995) and then undertook her first leading role as a sexually-precocious teenager in the overblown "Ripe" (1997). As the title heroine in "Snow White: A Tale of Terror" (Showtime, 1997), Keena proved a lovely presence and held her own opposite Sigourney Weaver who played her evil stepmother. Although "Strike/The Hairy Bird" (1998), a period film set in the early 1960s, received only a regional release, critics especially singled her out as the beautiful aspiring performer with slightly loose morals. That character could easily be a sister to Keena's rebellious Abby Morgan, a role she essayed with relish and wit before the character was phased out of the show.
Keena sparkled as pert, experimental college freshman Rachel Lindquist in writer-producer Judd Apatow's much-undervalued NBC sit-com "Undeclared" (2001-2002), snagged a role in writer Mike White and director Jake Kasdan's "Animal House"-throwback "Orange County" (2002), and leading her first scream-queen leading lady gig in the horror icon smackdown "Freddy Vs. Jason" (2003), followed by a leading turn in the lesser thriller "Long Distance" (2004). The actress displayed her quirky charms again in the otherwise lackluster comedy "Man of the House" (2005) opposite Tommy Lee Jones as the highly-strung, panic attack-prone cheerleader Evie.