Why does Mila convince herself that Selim is dead in the novel, We Were the Lucky Ones?

Selim is Mila's husband and Felicia's father. He is a doctor, and he goes missing after traveling to Lvov at the beginning of the novel. His absence weighs heavily upon Mila, who ultimately decides she must pretend that Selim is dead in order to get on with her life and protect herself and her daughter.