Chances are, this should not be enough to cause any issues.
Chocolate toxicity signs occur in three phases:
1. Mild ingestion- increased drinking/ thirst, vomiting, diarrhea, excitation
2. Moderate ingestion- cardiac arrhythmias
3. Severe Ingestion- muscle tremors, seizures, death
This amount of chocolate is unlikely to cause a problem in your dog. It's well below the dose that is needed for the cardiac or neurologic toxicity signs. You may see a little GI upset (mild diarrhea) and increased drinking/ urination for 1-2 days as chocolate is a potent diuretic.
If you want to give something for the vomiting, you can give Pepcid AC (Famotidine) at a dose of 0.25 mg per lb every 12-24 hours. If you want to give something for the diarrhea, you can give 1 teaspoon of canned pumpkin (for the fiber content) 2-3 times daily for 2-3 days.
Other than that, the main thing you want to do is offer small frequent amounts of water and make sure she urinates every 2-4 hours for the next 24-48 hours as chocolate can be reabsorbed over the bladder wall. If any neurologic signs (tremors/ seizures) then you have to go to an ER vet right away as these guys need Valium injections.
I hope this helps, let me know if you have any other questions.