Does she have a rash at all? My kids have just had slap cheek/hand foot & mouth. They had the rash, which I think must be hand foot & mouth, but when DD1 was little she had slap cheek & only had fevers. Her cheeks were red & she was off & there wasn't much else to it.
They are both strains of parvo virus.

How high are the temps? If they are over 39 I'd be doing my best to keep them lower. Keep a close eye on fluid intake & wet nappies as well. Its so easy for them to dehydrate.

Hope she starts feeling better soon xx