Hi jpouch mom,
so sorry to hear all this-it must be so hard to watch and live this as a parent 
It’s hard to tell from your post exactly what you need advice with-is it mainly the excessive output and pain? It makes sense she would lose her appetite -it’s hard to want to eat when you are sick and in pain.
My doctor gave me suppositories for rectal cuff inflammation that worked well for the inflammation-I think it was salofalk. If she’s always doing better on the antibiotics, do they think Pouchitis is at play? If her stools are improving on it it seems there would be a connection. Probiotics might help to restore some of the gut balance messed up from all the antibiotics for c diff.
i imagine others have suggested this but Metamucil really can be a god send to thicken things up. I also try a low residue diet if there is a lot of gut pain since it means things need to “move less” since there is less waste at the end. Lots of “bulky” foods like rice, pasta and bananas. It really sounds like your physician should be helping though-what are their thoughts? Gatorade for dehydration/electrolytes might help too.
good luck to you both-it does get better! I was close to your daughters age when I had my surgeries and missed 2 years of university for all kinds of similar pouch-related health challenges-spent nearly 6 months in total in hospital. Now it just seems like a blip and I got my life back for a good 20 years before having issues again. I lived with my parents for it all and know they felt very helpless. Hang in there....!