Sloane Matthews is played by Morgan Brittany in "The Protector", a.k.a. "Body Armor" (1997).
Beautiful Sloane is the asssistant of the main villain, evil scientist dr. Krago (Ron Perlman).
Near the end of the movie, Sloane pulls the gun to kill the hero (Matt McColm), but the good girl (Carol Alt) appears behind her, and shoots Sloane dead.