At first glance it seems odd that Melania Trump (a Christian) and Ivanka Trump (converted to Judaism) would both wear black and also have black lace headscarves to visit the Catholic Pope in the Vatican Rome, but would a few days previously not wear any headscarves in Muslim Saudi Arabia. It might appear that they are going out of their way to be incredibly respectful to the religious beliefs of Catholicism and less so to Islam.
But first appearances are not always completely what they seem. Female foreign dignitaries such as politicians or royalty are not required to cover their heads when they visit the Saudi Arabia- only Saudi nationals are. Meanwhile the Vatican (where the Pope lives) did speak of a dress protocol to Mrs Trump’s office at the White House, but no such requests had been made by Saudi Arabia. The Vatican website lays out some of the rules: modest dress, with your shoulders covered, for those attending a Papal Audience – especially if indoors. In fact women visiting sometimes wear deep lace mantillas to just a black veil. When the Queen went to see the Pope when as a young woman, she dressed up like the Spanish infanta, even though she is a Protestant Head of State.
Apparently Melania Trump, President Trump of the USA’s wife, asked the Pope to bless her rosary beads.