Could you have separation anxiety? All over the world 8 year olds are bringing up siblings. Try to realise that an 8 year old could look after herself if she had to. Give her responsibility, set her boundaries and expect her to keep them.
I always had a note on the wall/ fridge. Everytime something wasn't done I drew a cross. I threatened, after 5 crosses there will be some sort of punishment perhaps no TV, after 10 crosses then.... I hadn't decided what and it never came to that. The list on the wall was evidence of disobedience and somehow had to be faced up to. I started several for different things like brushing teeth or packing or unpacking a sports bag.
People eating and drinking on the go