What event creates a creates a permanent rift in Siddi's parents' marriage in the novel, Little Altars Everywhere?

Only when he is drunk can Shepley Walker find the courage to stand up to his wife. When his wife cuts her foot on a broken bottle, he tells her that she is a drunk. Even more insulting, he tells her that she is not a fit mother to their children. While both of these allegations are true, they create a permanent rift in the Walker marriage. Vivi Walker moves out of their bedroom and never returns.