In the sentence "The doctor phoned the nurse because she was late," the pronoun "she" refers to the **nurse**.

We know this because the clause "because she was late" explains the reason for the doctor's action. If the doctor were late, it would make less sense for the doctor to be the one initiating the phone call to the nurse due to their own lateness. The lateness of the nurse is a logical reason for the doctor to call.
