I agree with being an advocate.
Has she been checked by a nurse recently, is she keeping an fluid down?
My DS was taken to hospital on Boxing Day, years ago, by my (now ex) DH, because we couldn’t get his temperature down. He was 3.
I always did the hospital stays but DS had already been in hospital for a few nights that week with a chest infection, and I was so tired I let his dad take him.
When I got there I found DS in a side room, looking dreadful, and DH said they hadn’t seen a nurse for hours or a dr at all.
I went straight down the corridor and asked for ward manager and asked firmly for him to be seen. A nurse came straight away and they gave him a suppository (took a couple of staff as DS wasn’t happy and didn’t want to he touched 😞).
A dr then appeared quite quickly and they started DS on IV antibiotics.
Probably even more short staffed these days than they were back then and added to that there will be more people off with COVID and the majority of consultants take holiday over Christmas and new year (why the NHS is run like this I don’t know, if should be a 24 hour service for highly paid drs but then doing 9-5 week days) and anyone who tells you that the service is the same on bank holidays is lying.
Don’t be afraid to politely but firmly make a fuss - if you are really worried but aren’t getting anywhere then ask them to make sure they write in the notes that you asked for him to be reviewed, and what your concerns are. That usually speeds things up (spent quite a bit of time in hospital when DS was little!)
I hope your DD is feeling a lot better soon.