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It is not commonly seen but there have been people who have reported fainting/unconsciousness
for 60-90 seconds.This has happened in females achieving multiple orgasms or orgasm with over excitement.So i guess from the episode you have written it looks to be a case of what you can say a post orgasmic syncope
or fainting after sex.The wet vagina is due to excess of lubrication fluid released after orgasm may be even multiple orgasm.I guess there should not be a problem but just in case it happens repeatedly then get her examined by a Neurophysician to rule out an out side chance of epilepsy
which is a rare possibility and it is probably due to orgasm.