Thank you for your query on Healthcare Magic.
Your child seems to have a Viral fever
or Motrin for fever in prescribed dosage.
Give plenty of oral fluids to maintain hydration.
Provide rest to the child.
For vomitings and nausea, you can give an anti emetic like ondansetron
in prescribed dosage.
The weakness of the legs is due to the virus effects and it subsides once the viral activity decreases.
But physical examination of the child by her Pediatrician
is important to look for the focus of infection, hydration, and for prescription of medication.
Hope I have answered your query.