It is narrated from Sayyidah Khawlah bint Hakim (may Allah be pleased with her) that she asked the Messenger of Allah (peace and blessings be upon him) about a woman who sees in her sleep what a man sees. He (peace and blessings be upon him) said: "Nothing (is required) of her, just as when a man does not ejaculate, no ritual bath is required of him until he ejaculates."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20982