In fact, let's make the refusal even more explicit.
Let's suppose that he flat-out said, "I don't think she needs emergency care, and if you send this patient to the ER, I will refuse to treat her."
Even so ... isn't it ultimately on the NP -- who seemed to grasp that he was blowing her off -- to either get a second opinion or (ideally) use her own medical training to determine that the patient really should go to the ER, no matter what he says, knowing that he can't actually refuse to treat her?
Stating that you intend not to do something, after all, is not always the same as actually refusing to do it.
That's not the most compelling argument, I know.
But I do worry about the broader implications of this ruling. Should physicians fear malpractice claims arising out of consultations with colleagues? In what cases can you feel free to give your opinion "off the record," with the understanding that the person who has consulted you will bear ultimate responsibility for the treatment they are providing?