I don't actually think that doctor could refuse that workload, and I don't think I said that she could. The doctor culture is a unique one. Rotas are planned months in advance. They do not get changed. If you cannot get a mutually agreed swap for a shift that you want to be changed, you simply cannot have time off, and that includes annual leave. I have heard doctors say that they cannot get married, or can get married but must go on honeymoon the following month, because they can't get enough consecutive leave, as doctor x won't swap a shift and they have nights for 3 days that they couldn't swap in between wedding and honeymoon. It really isn't like nursing.
As a nurse, if I had a tricky rota (I say had, I have just started a role where I choose my own hours, within reason), and despite my requests going in, I found myself to be working on a shift that I had essential plans for, I could go to a Band 7 and say "arrgh!" They would request that I attempt to swap, but if I had attempted all feasible swaps, dependent on skill mix for the unit, and the unit could take a downshift in staffing on that day, or they were planning to staff up with bank on another day, for extra capacity, but could do that on that shift instead, they would.