Why does Edna get involved with Alcee Arobin?

By the time Edna leaves Grand Isle to return to New
Orleans, Edna has definitely concluded that she was not meant to be Adele Ratignolle.
She has fallen in love with Robert Lebrun; when he proves unavailable, she has an affair
with a womanizer named Arobin. She is clearly no longer prepared to subjugate all the
things she wants out of life to her husband’s ideal of the perfect marriage. She refuses
to entertain the wives of his business contacts; she disrupts the routine of the entire
household with her new avocation -- painting. The children are eventually taken to stay
at their grandmother’s, ostensibly because "the old madame . . . wished them to know the
country, with its streams, its fields, its woods, its freedom" but more likely because
she realized they were being neglected by their mother. Edna moves into her own
apartment, but is unable to find happiness there either, because even though she’s
learned who she isn’t, she hasn’t yet learned who she is. She eventually walks into her
beloved sea and drowns.