What do I do if a doctor fired me from her practice then is the only doctor who rounds at my rehab facility?

Find another doctor . Every doctor has the right to fire a patient for any reason as long as reasonable notice (3-4 weeks) is given. It is not his responsibility to find you a new doctor but he may. He is responsible to care for you for any emergencies for the notice period. It is your responsibility to find a new doctor, inquire about covered doctors from your insurance company. The rehab facility has its own doctors.