N'Soumer was born in the Kabyle village of Werja, from a Muslim marabout family, around the year 1830. Depending on the source, she is said to have had 4 or 5 siblings. Her father, Sidi Ahmed Mohamed, directed the Koranic school (Berber: timâammert) of Sidi Ahmed u Mezyan in the nearby village of Summer. Traditional sources agree that Fadhma showed a decisive and stubborn character from her early childhood. For instance, she insisted on following lessons in the Koran in her father’s school, very unusual social behaviour for a young girl in that culture.
Subsequently, being considered a tabudalit (a woman possessed by the Spirit), she followed a life of asceticism, committed to the practice and study of religion, and continued her studies at the timâammert in Summer. After the death of her father, his older brother Si Tahar, who was himself gifted with great charisma, took over running the school. Like her father and brothers, Lalla Fadhma was an adept of the mystic fraternity of Rahmaniya.
Soon after, it was said that Lalla Fadma had visions in which she had contact with wali, and that she was able to foresee the future. Her fame spread so much that Muslims from all Kabylie came to her to ask her advice and to offer her gifts. She received pilgrims in a room of the family's house in Summer, which still stands today.
To everyone, the young hermit seemed not only pious and wise, but also young and beautiful: she took great care of her body and clothes, and she habitually wore expensive jewelry. Everyone meeting her was deeply struck by these features.
A turning point in Lalla Fadma's life was the arrival in Kabylie, in about 1849, of a mysterious man who presented himself as Mohamed ben Abdallah (the name of the Prophet), but who is more commonly known as Bou Baghla. He was probably an ex-lieutenant in the army of Emir Abdelkader, defeated for the last time by the French in 1847. Bou Baghla refused to surrender at that battle, and retreated to Kabylie. From there he began a war against the French armies and their allies, often employing guerrilla tactics . Bou Baghla was a relentless fighter, and very eloquent in Arabic. He was very religious, and some legends tell about his thaumaturgic skills.
Bou Baghla went often to Summer to talk with the high-ranking members of the religious community, and Lalla Fadhma was soon attracted by his strong personality. At the same time, the relentless combatant was attracted by a woman so resolutely willing to contribute, by any means possible, to the war against the French. With her inspiring speeches, she convinced many men to fight as imseblen (volunteers ready to die as martyrs) and she herself, together with other women, participated in combat by providing cooking, medicines, and comfort to the fighting forces.
Traditional sources tell that a strong bond was formed between Lalla Fadhma and Bou Baghla. She saw this as a wedding of peers, rather than the traditional submission as a slave to a husband. In fact, at that time Bou Baghla left his first wife (Fatima Bent Sidi Aissa) and sent back to her owner a slave he had as a concubine (Halima Bent Messaoud). But on her side, Lalla Fadhma wasn't free: even if she was recognized as tamnafeqt ("woman who left her husband to get back to his family", a Kabylie institution), the matrimonial tie with her husband was still in place, and only her husband's will could free her. However he did not agree to, even when offered large bribes. The love between Fadhma and Bou remained platonic, but there were public expressions of this feeling between the two.
Fadhma was personally present at many fights in which Bou Baghla was involved, particularly the battle of Tachekkirt won by Bou Baghla forces (18–19 July 1854), where the French General Randon was caught but managed to escape later.
On 26 December 1854, Bou Baghla was killed; some sources claim it was due to the treason of some of his allies. The resistance remained without a charismatic leader and a commander able to guide it efficiently. For this reason, during the first months of 1855, on a sanctuary built on top of the Azru Nethor peak, not far from the village where Fadhma was born, there was a great council among combatants and important figures of the tribes in Kabylie. They decided to grant Lalla Fadhma, assisted by her brothers, the command of combat.
Defeat was inevitable for the Kabylie people, being outnumbered and outgunned by their enemies, and their villages and tribes fell one after another in just a few months. The first tribe to be defeated was the At Yiraten; on their territory the French started to build a fort (Fort Napoléon, named after Napoleon III) on June 14.
A strong defensive line managed to stop, with great losses and only temporarily, the attackers at Icherriden (June 24: 44 deads and 327 wounded) thanks to a sudden attack originating from trenches hidden in the terrain. Traditional sources tell that Lalla Fadhma took part in the battle and ordered that the fighters should be tied to each other with ropes so nobody was tempted to flee. In few days, however, using artillery, the French army managed to go beyond these defenses and on June 28 almost all the major tribes capitulated (At Yenni, At Wasif, At Boudrar, At Mangellat, among others). Lalla Fadhma was among the last to surrender, retreating to a village hidden by the hardest peaks of Jurjura, Takhlijt n At Aadsou, near Tirourda hill.
On July 11, the last village held by Kabyle rebels, Takhlijt n At Aadsou, was stormed by the French and conquered. The reports about the fight are not clear: it is reported that there were episodes of corruption and treasons, which is highly probable—moving in those regions without expert guides would've been almost impossible. Some French reports tell that it was Lalla Fadhma's brother, Sidi Tayeb, who sold his tribe and his sister in exchange for the promise to not harm the village where his sister and her troops were hiding. But it's more likely he just negotiated the surrender after the military defeat. However, even if there were any agreement, the French army didn't respect them, invading the village, sent off the men, and forced Lalla Fadhma to exit from the house where she was hiding with the other women and children.
Lalla Fadhma n'Soumer was taken as a prisoner together with about two hundred more women and children, who were sent with her to a detention camp at the Zaouia of Beni Slimane in Tablat, under control of a bachagha (local authority) loyal to French.
Lalla Fadhma, and her example of a steadfast and fearless woman, is still interesting at the present time; in fact when in 1995 her remains were transferred to the heroes' cemetery of El Alia, Algiers, the actual date and time of the ceremony was not announced in advance, but only told to the media what had been done after it happened. The Algiers authority were seen by the media as embarrassed to do this move just after passing a bill about Family Code which was extremely harsh with women; in this way, the authorities would not have to take care of possible "unpleasant" manifestations by the women's associations which find in Lalla Fadhma an important figure embodying a deeply independent and modern woman.