The answer to your question depends on your own perspective. The main character, Monique, spends most of the story in denial. Denial that her marriage is falling apart; denial that her daughers are happy and well adjusted; denial that her life is not the perfect existence she thought it was. In the end, she begins to accept reality and knows that she must face life alone. The reader is left to create that life for her. Do you imagine that she is incapable of making it on her own? Does she need a relationship with another man to make her whole? Or do you imagine her emerging as a stronger, more capable person, able to face any hardship now?

It is instructive to read the eNotes section on the author's techniques:

When reading A Woman Destroyed, it is wise to keep in mind that much of Beauvoir's life was dedicated to her philosophy and her political activism. Consequently, many of her texts feature the existentialist anti-heroine, l'amoureuse, a woman character who abdicates her autonomy and her capacity for authentic engagement with life and others in favor of slavish attachments to other people whom she falsely thinks that she masters.

In Woman Destroyed, Monique begins as that anti-heroine, but she seems to grow into a new person.