The drier the wine the better I would say. Red wine seems more prone to lower my blood sugars than white.
The problem with lots of boozing is that the alcohol gets precedence in your liver over other things so other functions can be impared whilst its there and if you have too much over too long then you are more likely to have liver problems.
However, I've got completely bored and annoyed with the government and the press fixation on how many units of alcohol we can or can not take. These units are plucked out of the air and not actually related to specific circumstances; some people shouldn't drink at all, some people can happily get by on far more than suggested. It's down to how one reacts to alcohol - if your mother in law is happy and apparently well on what she's drinking then that's really down to her.
Keep an eye on liver function when she get's her blood tests done (and keep in mind that Statins can cause an additional strain to the liver so that's something else to think about).
Now, whose round is it?
Dillinger