In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Question: 

What is incumbent on a woman to do if she has a dream in her sleep that she’s having sexual intercourse with a man?

Answer: 

If a man dreams in his sleep that he is having sexual intercourse with a woman, or if a woman dreams in her sleep that a man is having sexual intercourse with her, then there is no blame [i.e. sin] on them because accountability is removed from them in a state of sleep and due to their inability to prevent that. Allaah [The Most High] does not burden a soul beyond what it can bear. The Prophet [sallal-laahu-alayhi-wasallam] said: “The pen (i.e. accountability) is lifted from three (people): The sleeping person until he (or she) wakes up; the insane person until he (or she) returns to sanity and the child until he (or she) reaches the age of puberty”. (1) The one who sees such a dream should make Ghusl if he (or she) saw a discharge (i.e. sexual discharge). (2)

[1] Hadeeth reported by Imaam Ahmad; Imaam Abu Dawood; Imaam Nasaa’ee and Al-Haakim. It is an authentic hadeeth; see Irwaa al-Ghaleel of Shaikh Albaani..Number: 271]; [2] Fataawa Al-Lajnah Ad-Daa’imah 5/311]