Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Bianca is lethargic, and vomiting for 2 days, the contents of which now look green.
Dogs that do not feel well often hide and are lethargic, so along with her vomiting and not eating I think she's just trying to tell you that she doesn't feel well.
Dogs that have a gastrointestinal blockage or very abnormal intestinal motility often vomit green material as that is digested bile, bile that sits in the stomach for a while. Bile only refluxes back into the stomach when gastrointestinal motility is abnormal, such as with a blockage or poor gastrointestinal motility due to primary intestinal or metabolic disease.
Vomiting can be related to chronic pancreatitis, esophageal reflux, a dietary allergy or sensitivity, toxin exposure, a viral or bacterial infection, inflammatory bowel disease, internal organ failure, a full or partial gastrointestinal obstruction or even infiltrative cancers such as lymphoma.
Is she a pup that gets into things or eats things that she shouldn't?
Because she isn't eating or drinking I am very concerned about her. She will quickly become dehydrated because she is vomiting.
If she does go outdoors exposure to infections, toxins and eating things she should not are real concerns.
Ideally she would see a veterinarian since she is an older girl if this has been going on for more than 48 hours. Simple stomach upset should pass within 24 to 48 hours. They could examine her, run blood tests and possibly check radiographs and/or an ultrasound to evaluate her and know best how to treat her.
In the meantime they can administer injectable anti-nausea drugs and fluids to rehydrate her.
If you cannot have her seen for whatever reason there are some things you can try at home, though if she doesn't respond quickly she should see a veterinarian.
At home to try and settle her stomach you can give either:
1) Pepcid ac (famotidine) at a dose of ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 12 hours
2) Prilosec (omeprazole) at a dose of ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 24 hours
These are acid reducers and should help her feel better. They are quite safe and can be used for several days if necessary.
You can use a medicine syringe to try and force water into her orally.
A couple of hours after giving the acid reducer I recommend offering soft foods mixed with water to make eating and swallowing more comfortable.
If she is refusing to eat even soft foods you can try offering meat baby foods or a bland diet of 1/3 boiled minced white skinless chicken and 2/3 boiled white rice mixed with some low salt chicken broth to make it easy to lap up and swallow.
If Bianca continues to not eat and continues to vomit green material she should see her veterinarian or an emergency veterinarian for an examination, diagnostics and intravenous fluids and supportive care.
Please let me know if you have any further questions.