Thank you for your patience (as you can see I was typing quite a bit for you),
Now unfortunately, the dark chocolate bar alone is enough to cause severe toxicity for a dog her size. Therefore, we are at high risk of adverse signs here. In regards ***** ***** we can see GI signs (vomiting, diarrhea) within 2-4 hours post ingestion (so we aren't out of the woods with that yet). Furthermore in severe cases like this, there is a risk of this triggering an irregular/fast heart rate, abnormal breathing, tremors and even seizures (which can appear up to 12-36 hours post chocolate intoxication).
Therefore, as we are reaching the edge of our window for inducing vomiting I would advise doing so right now. To do so, you can administer 3% hydrogen peroxide orally at a dose of 1ml per pound. (2 teaspoons per 10 pounds of body weight). You can give it via dropper, syringe, turkey baster -- just we want to give it orally and get into your dog. After giving this orally, move her abdomen around or get her to walk about to get things mixing. This should usually lead to vomiting. If it is unsuccessful after 10 minutes then it can be repeated twice more. If you cannot do this or do not have peroxide on hand, then it would be worth considering having her seen now so that the vet can administer apomorhpine (a very strong injectable emetic). That way, the chocolate will be out and you will have the peace of mind that she won't be at risk of toxicity.
As well or alternatively (especially if you cannot get her to vomit but also has this is useful up to 8 hours) consider administering activated charcoal now. This is available from the pharmacy and works to bind any remaining material in her stomach. Make sure to get the gram strength and not milligrams (since otherwise you will need to open a lot of capsules to use). For activated charcoal, we tend to give 1-4 grams per pound is given every 8 hrs. This can be mixed with food or mixed with water to syringe in (do note that it stains, so keep it away from white carpets/clothes) and could just limit the risk of this chocolate causing her trouble.
Finally, since any dose can cause GI signs, you can take a few steps to settle her stomach. To do so, you can consider covering her with a antacid for the next few days. OTC options we can use here are Pepcid (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid) or Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac). After you have given this (and allowed 20-30 minutes for this to take effect) and then consider offering small, frequent meals of light diet (ie boiled chicken, white fish, scrambled egg, or meat baby food -- as long as its free from garlic or onion powder -- mixed with white rice) to keep her stomach settled while she gets over the GI effects of the chocolate.
Overall, the chocolate bar alone is a toxic dose for her. Therefore, in this case, it would be best to be cautious and proactive at this stage. Therefore, do consider inducing vomiting right away and treating with activated charcoal to limit her risks. Further to this, we'd want to monitor her for any adverse signs and consider a light diet if any GI signs arise for her. If you do see any of those toxic signs, then we'd need her to her vet for IV fluids + further care.
In this situation, just in case you do wish to see an emergency vet, you can check @ http://www.vetlocator.com/.
All the best,
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