Anti-supported. Chopin avoided mimicking them.

Chopin’s rejection of the local colorists had nothing to do with sentimental novels. In fact, Chopin liked how the local colorists’ style was different from that of sentimental novels. She rejected the local colorists because of their backward-looking focus on “women’s culture” and her discovery of the New Women movement.

The description of sentimental novels is introductory background about the context Chopin was coming from. It tells us what kind of literature she grew up with, which helps makes her literary journey—which went in a different direction from those sentimental novels—all the more interesting.

Nothing in the passage suggests a connection between nostalgia and excess, whether from Chopin’s perspective or anyone else’s. Chopin did believe that sentimental novels were excessive, but those excesses didn’t stem from any kind of nostalgia. It was the local colorists who were nostalgic, and their style was detached and crisp rather than excessive.

The author never takes the position that women’s literature was already flourishing, so these two sentences can’t be meant as support for that position.