If she hasn't eaten in 3 days and isn't drinking much she needs to see a vet.
This might be parvo, or distemper, or corona virus, or simply an overabundance of intestinal parasites making her ill.
She at the very least may need supportive care such as fluids or antibiotics to help her.
If it is parvo or distemper ask the vet about using Tamiflu a human antiviral med
www.marvistavet.com/html/body_oseltamivir.html
Hope this helps you!
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