First, if her stools look like blood or are black (digested blood), then we need to be careful. This is because that can be a sign of hemorrhagic viral or bacterial infections (ie Salmonella, Campylobacter, Hemorrhagic gastroenteritis, parvo, etc) but also stomach ulcers, stomach damage, and tumors. So, do keep a close eye and any more suspect stools and we'd want her seen urgently.
Otherwise, just to note, we can see this and nausea induced vomiitng and anorexia for a range of reasons. Our main concerns if this isn't bloody would be a potential bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items (ie toxins, plants, non-edible items).
With this all in mind, as long as she can keep water down, we can try some home supportive care to try to settle her stomach and get her feeling like eating. To start, if she hasn’t just vomited (since otherwise we’d need to rest her stomach for a few hours first), then you can consider treating her with an antacid. Common OTC pet safe options would be: Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), or Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet). Whichever you choose, we’d give this 20 minutes before food to allow absorption. Of course, do double check with your vet if she has a known health issues or is on any medications you haven't mentioned. Though would note that if you give this and she cannot keep it down due to nausea that is usually a red flag that we need to bypass her mouth with injectable anti-vomiting medication from her vet.
Once that has had time to absorb and she is steadier on her stomach, you can consider starting her on a easily digestible diet like cooked white rice with boiled chicken, boiled white fish, cottage cheese, scrambled eggs, or meat baby food (as long as its garlic/onion free). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset and less diarrhea. You can also add fiber (ie canned pumpkin, all bran) to these meals to bulk up her stools. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning her slowly back to her normal diet.
Since dehydration is a risk if Millie is drinking poorly, we need to keep an eye on her hydration. To check that she isn't dehydrated, there are a few things you can test. Further to checking for gum moisture, do make sure she doesn’t have sunken eyes and that she doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have her seen before this becomes an additional issue for her (especially as it is often dehydration that makes them feel unwell).
Overall, there are a wide range of agents could trigger this GI upset we are seeing but if you are seeing blood then we do need to tread with care. Therefore, we’d want to start supportive care to settle her stomach. If she cannot keep that or water down at any point, appears dehydrated already, we see more questionable stool, or doesn’t respond to the above within 12-24 hours; then we'd want to get her vet involved. They can assess her hydration, rule out fever, make sure there is nothing in her stomach that shouldn't be there (ingested or otherwise) or any sinister viruses or bacteria present. Depending on their findings, her vet can treat her with injectable anti-vomiting medication, fluids, appetite stimulants, +/- antibiotics to settle her stomach, and get her back feeling like herself.
All the best,
If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need as this is the only way I am credited for assisting you today. Thank you! : )