February 3, 2016—“One of two Egyptian music idols has just returned from Dubai, the other from Germany, to shoot a video for a duet sung in praise of a Cairo that they cannot actually stand living in,” wrote a young Egyptian dentist in a Facebook post that was shared more than 7,600 times and liked by 26,000 people as of Wednesday.

Are Ruby's critics an obstacle to her stardom, or does the controversy over her secular style eclipse the star herself? The music videos that established Ruby's fame feature pelvic-thrust dance moves and revealing costumes, which infuriate a growing number of Middle Easterners. But compared to the gyrations and attire of …