She isn't a woman, she is a mother.

The Father introduces the Mother to the company with this qualification in Act I. It would define the Mother's reality and define what she is as a Character. She is the consummate figure of grief, mourning the Characters' inexorable fate, bearing, its anguish, and serving as its horrified spectator. In this respect, she is not even a woman, but she is first and foremost a mother in anguish. Pirandello elaborates this fantasy of maternal suffering further in his preface to the play. There the Mother is posed against the philosophizing Father, incarnating nature without mind in her suffering—she suffers the torture of what has befallen the family without thinking about it as the Father does. Caught, like the other Characters, in the unchanging and inexorable reality of both her drama and role, she laments that she suffers her torture at every moment. Her lot as mourner is fixed for eternity.