My ds has had random very high temps, followed by very low temps on an off for over 6 months. He seemed happy and fine while they were happening until he had febrile convulsions frequently and was hospitalised several times as they shot above 40c. They appeared and dissapeared randomly nd frequently, and unless he convulsed he would act the same as normal mostly. For months he recieved No definitive diagnosis. We stayed a week twice as well as several overnights trying to get answers. He lost his natural appetite completely too which was hugely stressful. He had no inclination to eat at all. No hunger for days, we had to force him to eat and still he acted normal for the most part.
Eventually one of the paeds after yet another round of blood tests checked his immunity levels to pretty much everything and suggested that all he knew that might explain it was that the blood panel showed rota virus exposure which can in rare cases cause longer term asymptomatic fevers and 'post viral anorexia' (leaving he body with no natural appetite or hunger signals.) He said ds should loose the symptoms over approx 2 years. Ds was immunised for rota virus- so the paed suggested it was a vax reaction either from a dud vax or a severe reaction. We are still working with the drs on ds's appetite etc months later to keep him growing and healthy.
This may not be the case in your child, but i shared this story to let you know that if they are regularly feverish or you are worried get her checked out for peace of mind. We were treated like fools by the hospital and looked at with suspicion because there wasnt an easy answer- but we had reason to worry and perseverence finally gave us answers and help.
its awful when our kids are sick.