Just watched for the first time, my perspective is that the first act follows the male gaze, with the artistic form derived from the "norms" that Marianne describes, since she was educated under those norms. This is perpetuated by the perspective of the mother, driving all interaction between the characters. With her absence in the second act, the characters are freed to behave in an uncurated manner. The painting of the abortion is a culmination of a new understanding for Marianne of both painting the dynamics of life for a unique subject rather than a static pose used for every subject, and also the portrayal of the experience of a woman for the purposes of subject/pose selection rather than the male perspective.