Its better that you take her to ER.
It can well be a virus. But she needs to be examined as you say she is lethargic.
She might need medications for her vomiting- like domperidone
if she seems to have gastritis
Ear ache can happen in any upper respiratory infection
as middle ear is in continuum with our throat. In such a case doctor may give you decongestants and antihistamines too.
Till then keep her hydrated with fluids like water, juices, milk, soups etc.
Hope my answer helps you.
Wish a speedy recovery for your kid.