The negative feminine third-person forms keep the same feminine number endings as the affirmative forms. Mā is a separate particle.
TypeFirst formSecond form
Singularمَا فَعَلَتْ: she did not.مَا فُعِلَتْ: she was not acted upon.
Dualمَا فَعَلَتَا: the two women did not.مَا فُعِلَتَا: they two were not acted upon.
Pluralمَا فَعَلْنَ: the women did not.مَا فُعِلْنَ: they were not acted upon.
The endings ـتْ، ـتَا، ـنَ still distinguish the three feminine numbers, even after negation.