I am asking about the ruling on nurses not wearing an abaya.

A Muslim woman must wear clothing that covers her entire body from those to whom it is unlawful to see her, based on the Almighty’s saying: "O Prophet, tell your wives and your daughters and the women of the believers to bring down over themselves [part] of their outer garments. That is more suitable that they will be known and not be abused. And ever is Allah Forgiving and Merciful," and His saying: "And not display their adornment except to their husbands, their fathers..." [the verse]. Islamic law did not specify a particular type of clothing, but scholars have mentioned conditions that, if met in any garment, render it the prescribed Islamic veil (hijab (definition)).