Ms. Ayari, 40, is a fighter.

After the 2015 Facebook post, she went on to write a book, “I Chose to Be Free: A Survivor of Salafism in France,” which exposed the mental and physical subjugation that she and other women suffered inside the Salafi community. She also described a sexual assault, though she did not identify her alleged assailant by name.

That stance brought her threats and condemnation, even from her own family. She is not on speaking terms with either of her parents, and her eldest son, now 18, has sided with her Salafi ex-husband against her. Now, she has once again been subjected to torrents of online abuse.

She grew up in a working-class family in Rouen, the daughter of an Algerian father and Tunisian mother, both Muslims but not particularly religious. Her parents divorced when she was young and both remarried, leaving Ms. Ayari feeling insecure and unwanted.

She enrolled in college to study psychology and began to explore religion. She started to wear the veil and was quickly welcomed into a circle of conservative Muslims. Within months, they had set her up with a Tunisian Salafi who lived in Lyon. They married when she was 21.

One of the first things her husband, Bachir, did was buy her a jilbab, which covers a woman from head to toe, and a niqab, the veil that hides all but the eyes. The niqab was, in his words, the height of religiosity, the female garb that most pleased Allah.

For the next 10 years, Ms. Ayari lived a life of almost complete seclusion, bearing three children, sometimes spending days without leaving her bedroom and barely talking to anyone outside her husband’s family and immediate circle. Salafis teach that only they follow the true way, drawn from the time of the Prophet Muhammad. They reject association with those outside their sect.