How could Mary seek refuge with the Most Merciful from the angel Gabriel (peace be upon him), despite him being pious?

The verses appeared in the context of the story of Mary, peace be upon her, when she secluded herself from her family to the east, and took a veil to conceal herself. Then Allah sent to her the Angel Gabriel in the form of a human. She addressed him by saying: "She said, 'Indeed, I seek refuge in the Most Merciful from you, if you should be fearing of Allah.'" That is, 'I seek Allah's protection from you if you fear Him,' thinking he was a man from among humans. The conditional phrase "if you should be" was intended to incite the fear of Allah. Her mention of the attribute "the Most Merciful" and none other was because she wanted Him to have mercy on her by repelling the one she feared, and thus mentioning this attribute was appropriate.