Cheryl - you should consider consulting with an experienced injury attorney on this matter. Your chancesof prevailing an a liability case against the dog/property owner are good if handled properly. The issue becomes whether or not you have significant damages as a result of the incident.
I'd recommend you ask to speak with your client/co worker's insurance company. If she won't give you her insurance information then hiring a lawyer may be the right next step.
I recently had a similiar situation where my client was getting no where. I sent numerous letters which were ignored. Finally, I had to draft a Summons and Complaint and told the dog owner I was going to file it within 10 days if I didn't hear from them or their insurance company. I heard from there insurance company within the week.
In order to have an attorney's help you'll need to sign a retainer and meet with the lawyer in order to fill out additional paperwork. At that point you have "retained" an attorney and that attorney can send letters, make phone calls and try to settle the case pre-suit.
Most attorneys will meet you at a place convenient for you.
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