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. . . .