I don't think that Mrs. Baroda betrayed her husband. She certainly has thoughts of deception but the author is interested in exploring female sexuality. Like most men, Chopin is pointing out that women have thoughts too that do not necessarily mean moral transgression.
As in the case of La Folle, the protagonist in "Beyond the Bayou," many of Chopin's female heroines triumph by challenging, transgressing, or overcoming boundaries, and Mrs. Baroda is no exception. Her boundaries are implemented through the social idea of respectability.
Notably, Chopin never introduces Mrs. Baroda's first name, suggesting that she has previously identified herself in terms of her attachment to her husband, but it may be that her future affair will allow her to reclaim a stronger individual identity and sense of self.