Sheva Alomar is known to be one of the main characters in Resident Evil 5 (she is also a new character to the series), who will assist Chris Redfield in the game. Sheva is also likely left handed based on how she holds weapons in various screen shots.
Sheva joins B.S.A.A. after graduating University, the specific reason for her joining B.S.A.A. is because of her parents which were killed in a similar accident like Raccoon City.
Sheva Alomar is also in The Mercenaries Mode from Resident Evil 5.