Thank you for your query,
Your child looks to have severe gastritis
with persistent vomitings.
To control vomitings , antiemetic like ondansetron
should be given in prescribed dosage.
Give sips of oral rehydrating solutions like ORS, coconut water, lemon water should be given in equal amounts the losses in vmitings.
Monitor her hydration status by skin turgor, urine output, activity and tongue & oral cavity.
The rash should be examined clinically to find out the cause for it.
Consult your Pediatrician
for assessment and proper management.
Hope I have answered your query.