Keep your daughter wrapped up when she goes outside and put a scarf around her mouth and nose so that she does not breathe in the cold are.
At home, keep her comfortable and offer her plenty of warm drinks and her favourite soup. If she likes jelly make her some of that, anything as long as she is getting her fluids and does not become dehydrated. Although you need to keep her cool to bring down her temperature, do not allow her to sit in a draught.
Hypoglycaemia is when the body's sugar levels drop very low. Make sure that she eats little and often rather than a large meal at one sitting. In between meals give her a healthy snack like yogurt or fruit. Give her foods that are slow energy release, like porridge, fruit, vegetables, brown bread. Nuts and pulses are also slow energy foods.
Sweets, cakes and biscuits are quick release energy foods because they are highly processed and refined. Eating these types of foods will spike the sugar level up very quickly, but the blood sugar level will also drop very quickly too. Because she gets low sugar levels, make sure that she always has some healthy food to eat should she start to feel hungry or sick or headachy. Digestive biscuits and glucose sweets are OK as a temporary measure a piece of fruit is a better option.
Wishing her a speedy recovery.
Not certain where you live but I do know that this year and a good part of last year there have been many respiratory issues in children and adults,.doing some research I noticed that there was mention of a new coughing virus also Docs do not know much about it .Allergies are another possibility..persist with having any tests done and look up any virus going around where you live,,Good luck