I would say Lorie Griffin who plays Pamela Welles in Teen Wolf! That scene in the dressing room when she seduces Michael J. Fox she looks amazing.
I also say Melora Hardin. Okay she is in the American Office, but I am thinking of her with her original hair colour(brunette) in the film Soul Man. She looks amazing in that.
For British actresses I would say Tara Fitzgerald. She looks amazing in The Englishman Who Went Up a Hill but Came Down a Mountain and Sirens. I would also add Natasha Little(Greenfingers, The Criminal, The Clandestine Marriage).