In which of their plays did the Rahbani Brothers portray the "Saint Barbara" festive LEBANESE traditions?

In one of their great plays Fairouz in heading to a city "Selina" to sell masks for the feast of the "Second face"and she get mistaken for a princess, and all the citizens try to convince her to keep up the charade in order to make profit of the king, great music, great writing, what was that play?