It seems like you need a few answers:
Transferring cancer patients to other care facilities of any kind can be risky to the patient, and if the doctors are not
accepting the transfer, you need to ask why. It could be for many reasons, such as: that she is at extremely high risk based on her medical condition, age, or prior treatment history, that she is not stable enough to move, that they have no available beds, or that they don't offer the treatment she needs. What prognosis have they given to your mom? If she is advanced, they may not want to offer future treatment to protect her current quality of life. They are supposed to be compassionate, and may be showing it in another way -- Neither of you wants to make it worse for her.
In terms of clinical trials, experimental treatments, and complementary therapies, there are many, many options for cancer patients. Get specifics on her disease from her oncologist and do some research. Remember, to participate in these programs, she must meet their criteria, but you are right, there is always hope.
Lastly, if you do find a treatment center or study center, there are companies that help transport. Air transportation can often be arranged through www.corpangelnetwork.org; ground transportation may be arranged through various St. Stephens shuttles, or Visiting Angels could help you move your mom.
It's easy to get discouraged but keep trying.