Who is Celeste Zachariah from The Murderer's Daughters and what is their importance?

Celeste Zachariah is Joey's wife. She is only twenty-six at the start of the novel, and she is described as a beautiful woman, who's been told that she should have been an actress. Instead, Celeste became pregnant at the age of sixteen and got married. She is now the mother of two little girls, and she is stuck in an unhappy marriage..... often entertaining other men when her husband isn't around. Whe her husbamd catches her cheating, they separate. Celeste later steals one of Joey's paychecks, an act that leads to her death.