How do I go about finding a doctor who can assess the care my mother is getting at rehab center?

She does not have a primary care physician as of yet....her last one died and she got sick before we were able to get a new one identified. She has increased swelling in her legs, ankles, feet and they don't seem to be overly concerned about it, but it is preventing her from being able to fully participate in the P/T services and the insurance company has declined her now becuase they say she should have progressed more by now. But our argument is that she hasn't been treated for the underlying cause of her swelling, so how can she walk? I need to find a doctor that would come in the review her care and see if there is anything different the doctor at the facility should/could be doing. We are also trying to appeal wth the insurance company has decided. Any advice?