Interesting. I think Abby was wrong, and quite unnecessarily rude and judgmental in her comments about calories, which makes me want to wholeheartedly disagree with her :-) BUT - polite behaviour is, in part, about making not making other people uncomfortable, and I can understand that LW dining companions might feel uncomfortable, if they are shy or self conscious, and felt that LW's behaviour drew attention to them. It's not quite like being at the table with the person who is inappropriately loud or obnoxious to the waiter, because there is nothing inherently rude about eating the meal back to front, but I think it could create a similar feeling of embarrassment / discomfort to fellow diners.
Of course, it's rude of the coworkers to criticise, either way.
The only time I think it would be rude would be if eveyone else wanted a quick snack, and LW is going to 2 full courses,but it doesn't sound as tho that is the case.