ok, now I'm trying to guess/remember names
It is worrying, of course it is, poor you and poor dd. Lack of sleep doesn't help with worrying, either.
We gave her full formula feeds (stopped bfing a few months ago) as per current guidelines, plus water, and after a few days of runs gave diarolyte in water, as much as she wanted, offered every hour. We also offered solids, but she wasn't interested for a few days. dd was vomiting occasionally as well (big vomits) but as she has reflux, she's sensitive when unwell so wasn't sure if that was part of bug or not.
Do give her acidophilus, though - if her guts are upset due to bug OR antibiotics, they can only help re-establish things asap.
If she's dehydrating, you will be able to tell by sunken fontanelle (if not closed yet) and/or if you gently pinch a bit of skin on back of hand, it should drop straight back down. If it stays up in a ridge, she's too dry. If she's really dehydrated, she'll be lethargic/irritable too - but as she's got a fever, its so hard to tell with that particular sign.
If you do think she's dehydrating, I'd go to A&E or call out of hours doc....not worth messing around with, IMO. Neither is your peace of mind!
And I'd alternate Calpol and Baby Nurofen for the fever, if its that high. GOod luck, let us know how she is, xxx