My mental association is that of alcohol being regarded as having healing powers and useful in cases of shock. You know that cliche of St Bernard dogs finding people lost in the snow, and the dogs wear collars with a small barrel containing some brandy, given the lost traveller the strength to stumble to their feet and follow the dog to shelter.

And Marianne's treatment struck me as falling into that category, the wine being given as a quick restorative.

Alcohol is one of the relatively few substances that gets past the blood-brain barrier to affect behaviour, so it's not surprising that it got prescribed for mental shocks.