The Prophet ﷺ was asked about a person who found moisture (on his body or clothes) but did not remember the sexual dream. He replied: He should take a bath. He was asked about a person who remembered that he had a sexual dream but did not find moisture. He replied: Bath is not necessary for him. Umm Salamah then asked: Is washing necessary for a woman if she sees that (in her dream)? He replied: Yes. Woman are counterpart of men.  

سُئِلَ رَسُولُ اللَّهِ ﷺ عَنِ الرَّجُلِ يَجِدُ الْبَلَلَ وَلاَ يَذْكُرُ احْتِلاَمًا قَالَ يَغْتَسِلُ وَعَنِ الرَّجُلِ يَرَى أَنَّهُ قَدِ احْتَلَمَ وَلاَ يَجِدُ الْبَلَلَ قَالَ لاَ غُسْلَ عَلَيْهِ فَقَالَتْ أُمُّ سُلَيْمٍ الْمَرْأَةُ تَرَى ذَلِكَ أَعَلَيْهَا غُسْلٌ قَالَ نَعَمْ إِنَّمَا النِّسَاءُ شَقَائِقُ الرِّجَالِ