It was narrated from Khawlah bint Hakim that:
She asked the Messenger of Allah about a woman who sees in her dream that which a man sees. He said: "She does not have to take a bath unless she has an orgasm, just as man does not have to take a bath unless he has an orgasm." (ES)
English reference (ES): Vol. 1, Book 1, Hadith 602 (ES)
Arabic reference (ES): Book 1, Hadith 645 (ES)