In 1986, Donna Murphy was a woman in drag in “The Mystery of Edwin Drood.” In 1991, she was introduced as “a girl who will steal your heart and then forget where she put it,” playing the amnesiac songstress in “Song of Singapore.” Having become one of Broadway’s most sought-after actresses, Murphy is now playing the lead in Stephen Sondheim’s latest musical, “Passion.” Of the role, which has her playing an ugly, hysterical woman obsessively pursuing a handsome army captain, Murphy says, “I love transformation of any kind...I want to look in the mirror and not see Donna looking back at me.”<