My own DD has ongoing tummy trouble as part if another health condition, so I have learnt how best to deal with this naturally & have had hospital advice too.
You need to stop all roughage goods for a few days & get her eating white stodgy stuff - the opposite of the usual healthy diet - it might be worth cutting our wheat for a short while too - so white rice, mash potato
She also needs to top up the tissue salts she has lost with the diarreah - these are needed to hold the fluid in her body, without this the diarreah will continue - ideally Diaralyte is best, though its nasty stuff, the lemon is easiest to take - if you really can't get this down her - then coke ( for glucose), plain crisps (for potassium & sodium) & bath grade Epsom salts - 2 cups in a bath or foot bath & let her soak for a while - this will get magnesium into re system.
Turmeric is a fantastic medicinal spice & it soothes inflammation in the gut - you could add a spoonful of this to the cooking water of her rice & manuka honey is great for the gut amongst other things too - give her a spoonful to eat.
Apple juice is laxative - so avoid
Milk can bind her, so can be good to stop diarreah, unless there's any chance of lactose intolerance which will be worse during times of tummy upset -
if there is buy Lactolite milk, is in all the supermarkets so way to find
Avoid fruit for a few days
Veridians children's flora powders are good for restoring the good gut bacteria.
& a long shit, but worth mentioning as it happened with my own DD & it took months before we realise - no doctors, not even the Gastro did 
- has she recently started or upped the dose of an asthma inhaler ?? - if so that can be your culprit
Hope she's better soon & you all get some rest 