ROSALIND
Love is merely a madness; and, I tell you, deserves as
well a dark house and a whip as madmen do; and the reason why
they are not so punish'd and cured is that the lunacy is so
ordinary that the whippers are in love too. (3.2.44)
Rosalind really does believe love is a madness; she is not just speaking in jest here. One of her intricacies as a character is to admit that love is madness and still be perfectly happy to get caught up in it (something someone like Jaques could not do).