I think Sunset Blvd would be too close to the Black Swan--a character teetering over the edge into insanity. I was thinking more along the lines of Double Indemnity or The Maltese Falcon--the femme fatale who appears to be something she really isn't. And there are plenty of moody jazzy/bluesy and/or classical scores from that period. Think Kathleen Turner in Body Heat. Sexy and dangerous. I could see her doing something along those lines.