Have you tried crushing the chewable vitamins and sprinkling the powder (and mixing it) into her food? Possibly if she doesn't know it's in there she'll eat it.
I've had lots of problems with yeast infections and have to say with the precautions you're taking to prevent them they more than likely are being caused by her diet. If she eats peanut butter try eliminating it from her diet to see if that helps. Peanuts & peanut butter are notorious for having mold and causing yeast infections, unless it's guaranteed organic peanut butter or peanuts.
http://www.youryeastinfectioncure.com/Yeast-Infections-in...
There's lots of other foods that yeast feeds on and can promote yeast growth and lead to an infection:
Hydrogenated oils
Sugars ~White sugar, Brown sugar, Syrups, Honey, Fructose
Sorbital ~ (I've seen this used in sugar-free lollipops for kids at my pediatrician's office)
Dried fruits and fruit juice
Vinegar and condiments containing vinegar (ketchup, mustard, mayonnaise, salad dressing)
Starches/pastas
Refined carbohydrates
White flour & white bread
White rice
White potatoes
Grains
Yeast and yeast containing products
Mushrooms
Bread
Cider
Fruit skins
MSG (often extracted from autolyzed yeast extract or from wheat)
Yeast Extract
And, bananas have been found in recent studies to be one of the highest contributing fruits to Candida (yeast) and should be avoided altogether for those of us who are highly susceptible to yeast infections.
http://www.articlesbase.com/nutrition-articles/risk-of-ba...
I hope some of this helps, I so feel for your daughter and hope you can find a way to stop her infections.