I've seen a couple of studies that said there were no links between dairy and 'mucus' or respiratory infection and so on. Sorry no links, but if you go to google scholar you might find something useful.
You might find that some probiotics will help; I've got some Blackmores brand ones which are actually pleasant and chewable (thinking here about restoring oral flora).
Could there be something in her environment that is triggering it? Bedding, pets, carpeting, plants? Birch trees?
If we’re not supposed to eat animals, how come they’re made out of meat? Tom Snyder