What does Grace tell March about the true nature of Mr. Clement’s son’s death?

. When March suggests that Grace has nothing to feel guilty about, she stands up straight and tells him that a few months back, she shot and killed her brother, Clement's white son, when he tried to rape her. March tries to tell Grace that she had no other choice, but she snaps that she is not searching for March's absolution. She tells him to go home; she does not need him.