Is it legal for the only Oncologist in the county to deny you service after being an ongoing patient for years?

My mom has had cancer for almost 10 years...she has beaten 5 different types and is now suffering from lung and liver cancer. Her doctor gave her a 30 day notice this past week saying that he will not treat her anymore after 30 days. Siting inappropriate outburts and refusing consultation as grounds. My mom said she was at the emergency room all of Thursday with severe stomach cramps, this is how she found out she had colon caner about 10 years ago. Well she had a Chemotherapy infusion on Friday and that takes about an hour and the doctor was supposed to come down and talk to her, well after waiting 4 hours she said "i just want to get the f*** out of here" not angrily just out of frustration to the nurse the nurse said "I completely understand you were here most of yesterday as well!" so she tried the doctor again and got no response so my mom left. Well my mom got a call from the doctor's head nurse about 3 hours later and she told my mom she had to come pick up her records and explained that my mom had 30 more days of treatment there and she needed to find another oncologist. My mom is well below the poverty level for income...the state wouldn't let her get disability because she beats a cancer then gets a new one but with little to no downtime between the outbreaks. Her sole income is from social security and she had to fight to get that. She can not work since she has chemo and radiation therapy multiple times a week. She also just lost her house where she lived for 20+ years. I've tried looking at the Code of conduct and some of the legal guideline but its extremely difficult to find what im looking for, and I am not versed in "legalese" so most of it makes little sense to me. So I turn to you Yahoo answers community to help me out...any help is desperately needed and would be greatly appreciated!