I haven’t read Mary Ann Doane’s book, but in my experience film noir femmes fatales don’t tend to be particularly promiscuous — certainly no more than their male victims (e.g. Phyllis Dietrichson in “Double Indemnity.”) And in
“Double Indemnity” and “Body Heat” the femmes fatales may incite their partner / victim to murder, but the men are no less innocent, just more gullible. The femmes fatales in “Scarlet Street” and “The Lady Eve” are essentially faithful to their male partners in crime, fleecing their victims by means of their attractiveness but not necessarily having sex with them.

And femmes fatales don’t indulge in sex out of hedonism. Sex is a way of gaining power and/or financial independence denied them by the patriarchy (Bridget Gregory in “The Last Seduction”). This is why the femme fatale doesn’t opt for marriage with children.

The fact that most femme fatales either fail in their quest for power (gruesomely in “Freaks,” for example) or repent out of love (“The Lady Eve,” “Ball of Fire”) may be Hollywood’s way of suggesting that women who attempt to subvert patriarchy will not succeed, but their failure doesn’t mean they didn’t try. On occasion (but rarely) some femmes fatales do beat the system.