QuestionWhat about us girls reaching orgasm while sleeping? Is it sinful? Why does it happen?
Sin is when you choose to break a law of God. "Whoever commits sin also commits lawlessness, and sin is lawlessness" (I John 3:4). Things that happen in your sleep are not by conscience choice and so are not sinful.
Orgasm while dreaming happens to most women. It isn't always noted since you are sleeping at the time and you often sleep right through them. The same thing happens to boys, by the way, but since ejaculation occurs with orgasm, even if they sleep through the event there is evidence that it happened when they awake in the morning. Such isn't the case with women. Because of this, less is known about female orgasm during sleep. Most women only notice that it happens once a year or so, some notice it several times a year, a few notice it more often. I suspect much depends on how light of a sleeper a person is.
The reason for the orgasm would probably be much the same as why boys get spontaneous erections. During your dreams, you are in the Rapid Eye Movement stage of sleep. It isn't just the eyes which move, the brain during dreams moves other parts of your body. At times the brain triggers the sequence needed for orgasm. In a sense it is like a systems check where a quick practice run is done to make sure the various sequences needed are being done right.