Asssuming the article is accurate, I think you're mis-characterizing what happened here. Simon wasn't calling a colleague for a second opinion before making a decision; she decided Warren needed to be admitted, called a senior hospitalist to expedite that admission, and was clearly and repeatedly refused.
The OP's title "doctors can be sued by patients they don't treat" is not accurate. A better one might be "doctors can be sued by patients they refuse to allow treatment."
The OP's title "doctors can be sued by patients they don't treat" is not accurate. A better one might be "doctors can be sued by patients they refuse to allow treatment."