Later, Viola's twin brother will show up and accept the love that Olivia felt for "Cesario/Viola." Eventually, everyone receives love, "sought," or "unsought" (the best).
Olivia is not being ironic, but there are ironies in her statement. She has refused "unsought love" from Orsino, but she wants "Cesario/Viola" to accept "unsought love" from her. And Viola's love for Orsino is "unsought" by him.
Later, Viola's twin brother will show up and accept the love that Olivia felt for "Cesario/Viola." Eventually, everyone receives love, "sought," or "unsought" (the best).
Imogen Stubbs as Viola, left and Helena Bonham Carter as Olivia, right—1996