After some detailed research (about two minutes, actually, and it was time mightily well-spent) I found a possible explanation here. Yes, apparently some researchers discovered that the "phenolics" in cider have a beneficial effect on health. Who knew?
I can only conclude that Becky's whopping consumption of cider somehow counterbalances the effects of the voddies and fags, not to mention the "full cookeds" at Roy's. Hmm.