Hi, I am Dr. Peter and would like to help. In response to your question, this is not a toxic dose for her weight. She would need around 10 ounces. The worst case is mild diarrhea. If she does get diarrhea feed her a bland diet of rice and chicken. She will be fine.
Symptoms of chocolate toxicity usually start within 2 hours and they start with hyperactivity, vomiting and eventually can lead to heart problems.
If you have additional questions I will be glad to answer them.