The affectionate term "Holy Mother" refers to Sri Sarada Devi (1853-1920), Sri Ramakrishna's wife and spiritual counterpart. According to the custom then prevalent in India, she was betrothed to him while still a child. At the age of 18, she left her parental home to join her husband, who lived some sixty miles away, near Kolkata.
By that time Sri Ramakrishna had dedicated his body and mind to the spiritual search and lived the life of a monk. Yet he received Sarada very kindly, feeling that Divine Providence had brought her. After nursing her to recovery from an illness contracted on the journey, Sri Ramakrishna one day asked her why she had come to join him.
She replied that she had come only to help him in his chosen way, which---as she well knew---meant the way of complete renunciation of all earthly ties for the sake of God-realization. Thus, instead of seeking conjugal fulfillment, she became his first disciple.