Excuse my cynicism here, but there is no way that an Israeli director (who has actually directed a movie about Israeli Haredi life) did not know that filming a scene with two people kissing passionately by the Kotel, without prior arrangement, would not end in the exact scene which did, in fact, occur ("Ultra-Orthodox nearby took notice and rushed toward them with shouts of “Immoral! Immoral!").
My guess is that Director Amos Gitai needed that scene for the movie and didn't fancy hiring extras. When the movie's released, I'm willing to bet (albeit not a lot...) it'll contain a bunch of Ultra-Orthodox men rushing towards the characters played by Natalie Portman and Aki Avni, shouting, "Immoral! Immoral!"