My wife woke up and found that in her sleep she had gotten her period. Does this count as the night onah or does it go from when she saw it in the day time?
It is a day onah, because it goes from the time that she noticed it. The reason for this is because we assume that she remained tehora until she actually sees.
Eshkol-32, Badei Hasulchan 184-31, Poskim.