The Two Mrs. Grenvilles by Dominick Dunne

When Navy ensign Billy Grenville, heir to a vast New York fortune, sees showgirl Ann Arden on the dance floor, it is love at first sight. And much to the horror of Alice Grenville—the indomitable family matriarch—he marries her. Ann wants desperately to be accepted by high society and become the well-bred woman of her fantasies. But a gunshot one rainy night propels Ann into a notorious spotlight—as the two Mrs. Grenvilles enter into a conspiracy of silence that will bind them together for as long as they live. . . .