This scene is of course the parallel scene to the prior gulling of Benedick, where he is made to believe that Beatrice is desperately in love with him. The immense humour in this scene lies in the way in which we know that Hero and Ursula are aware of Beatrice's presence, but Beatrice does not know that, and continues to believe that she is eavesdropping upon them unbeknownst to them.
Many productions therefore deliberately play on this differing perspective, showing Ursula and Hero spying on Beatrice before entering in upon her location, remaining blissfully unaware of her presence even in spite of Beatrice's clumsy attempts to keep up with them and listen to their conversation. One production I saw, for example, used a maze in a garden to stage this scene, with Beatrice obviously sticking her head over the top to try and keep up with Ursula and Hero. The fact that the maze was only waist-high, and so Beatrice had to crawl around on hands and knees to keep up, only added to the comedy. Such a setting allows the humour of the scene to be indicated whilst making it absolutely clear to the audience that Beatrice is being tricked.