When she arrived at the border, she asked the border guard to be allowed into Saudi Arabia. The guards confiscated Ms. Hathloul’s passport and forced her to wait overnight in her car.

After she chronicled her ordeal on Facebook, and told readers of her Twitter feed that she was cold and hungry, another Saudi national living in the U.A.E., Ms. Amoudi, drove to the border to bring supplies to Ms. Hathloul.