She was played by Paula Garcés.
Paula Reyes is a police officer who was previously in a romantic relationship with Detective Marcus Bell, until she learned that Bell was the one who informed Internal Affairs about her corrupt superior. The superior was her top supporter regarding a promotion, most likely because she helped him plant evidence to get Bradshaw, a local drug dealer off the streets.
Paula turned villainous and sought revenge on Bell, beginning with shooting and killing Bradshaw. After that, the evil Paula shot Bell's brother, Andre, and tried to frame Bell for the crimes. Paula is eventually caught and arrested, but not before she delivers one final parting shot to her ex-lover, stating that she's not surprised that he wasn't there during the summation because saying things to her face "wasn't his style."