But then

Does the bold section mean "in masquerade (disguise) women try to mimic a genuine womanliness, while the authentic womanliness is nothing but the mimicry and the masquerade itself"?

Context:

Now while this might all seem a bit farfetched when thinking about art practices such as Sherman’s and Cahun’s, the upshot of Rivière’s paper, that womanliness was synonymous with masquerade, was seen as a useful reading of their work. Sherman’s images were celebrated by critics as exemplifying Rivière’s dictum that ‘n the masquerade, the woman mimics an authentic – genuine – womanliness, but then authentic womanliness is such a mimicry, is the masquerade.’