You poor thing! It is hard enough to run the diagnosis gamut for yourself, but to have to do it with your daughter... :(
You have to be persistent. It takes many people years of searching before they find a doctor who can help them. You may be able to find someone on one of the forums who can recommend a good doctor in your area, and you may need to consider looking in a different city if yours doesn't have many options. I live in a small town so I drive an hour to visist my doctors, but it is well worth it for the premium care.
You may want to consider putting your daughter on a B12 supplement, that way the doctors can't use her deficiency as an excuse to ignore her pain.
Just be there for your daughter. With all of these doctors telling her the pain is in her head, she really needs you to fully support her and let her know that someone believes her.
I pray you find a good doctor soon.