Helena responds to the new admiration of Demetrius and Lysander for her as though they are mocking her. She has good reason to believe this, as Lysander and Demestrius have both, more or less, ignored her up until this point. Furthermore, Helena believes that Hermia has put the two suitors up to this mockery. In short, she responds with hostility. One of the important elements of the play that this entire episode cleverly dramatizes is that the lovers--Demetrius, Lysander, Hermia and Helena--are all basically interchangeable. Sometimes they hint at this themselves; Lysander, for instance, hints at this in the first scene: "I am, my lord, as well derived as [Demetrius]/As well possessed" (1.1.99-100).