You can also boost her immune system by helping her gut (something like 80% of the defense system is there) with probiotics. Get some good stuff from a naturopath which you can sprinkle on food, or put in yoghurt. Yoghurt has some naturally but not in good sized doses. Also many brands are fast tracked with faecal matter and made other ways. Fast Tract or In-Liven is great stuff, but it's not the cheapest of them all. You get what you pay for though Garlic is also great, its 3 in one, anti bacterial, fungal and I think viral. Onion also good. All the usual antioxidants (A, C & E vitamins) are good.