If you do want to continue perhaps write a letter explaining your thinking at the time and your fears and emotional state that was involved in how you approached her.
What I get reading between the lines is the need for trust between the patient and oncologist and perhaps she feels this isn't there.
So ask yourself...do you trust her decision making / knowledge / experience?. If you do , then tell her. Sometimes specialist need time to ponder a course of treatment action and at that time wasn't certain which way she would go. It's possible your response on that day was insulting to her knowledge without intention. But a heartfelt apology may be accepted and the working relationship can then continue.
I hope tbat you have a new specialist soon and feel confident in your treating team. Kath x