NICE guidance (March 2008) is:
Advise women planning a pregnancy to avoid alcohol in the first 3 months if possible.
If women choose to drink alcohol, advise them to drink no more than 1 to 2 UK units once or twice a week (1 unit equals half a pint of ordinary strength lager or beer, or one shot [25 ml] of spirits. One small [125 ml] glass of wine is equal to 1.5 UK units). At this low level there is no evidence of harm.
Advise women to avoid getting drunk and to avoid binge drinking.
So not a straight up "don't drink" message, but given the range of opinion as to what might be considered heavy drinking, and the preponderance for pubs to supersize drinks I don't think it is unreasonable to think that people might be confused as to what constitutes a unit, so many doctors/MW in practice may give the easier message "don't drink"
If the large glass is actually close to a third of a bottle of wine (3-4 units), then I personally would think that was at least a moderate drinking habit. If this was my friend I would talk about it to her, yes. I wouldn't nag, because that is completely pointless. Personally I drank small amounts of good wine (probably about half a glass) when offered, but only in the middle trimester.
Oh, and if you want to look at evidence, then the NICE site gives a summary of all the evidence used in putting together their guidance (which is part of general advice on antenatal care). www.nice.org.uk/nicemedia/pdf/CG62EvidenceTables.pdf The evidence, such as it is is quite equivocal, and as true double blind tests are obviously impossible, it's probably not going to get much better. But unless you are qualified in statistics, epidemiology and critical appraisal then I think it is foolish to dismiss the NICE guidance in favour of your own research or feelings about your own reactions. It is likely that the researchers who produced this guidance probably do know what they are talking about (it is after all what they have spent their professional lives specialising in). I have a masters in public health and still found working out which research was credible and which was flawed very difficult (not that I was a star in my studies, but it is a complicated field).