But will she? Maybe she’s done this nightly, for the past decade, whereas your attempts to rescue her could waken her - which, with somnambulants, can cause disorientation and violent reaction - could be the cause of her fall.

In this case, action should be taken after she can safely be secured. Of course, this is a painting, of a maybe hypothetical situation, in a time long before sleep studies. So solutions of the time are likely going to involve morphine or some other heavily sedating drug, or maybe some form of at least nightly incarceration, if she’s lucky.