As long as she's only a background character in the visit to the Elevenking's halls in Mirkwood I can deal with it. If you can accept adding Legolas then other Elves not seen onpage would be fine with me as long as they're not too disruptive.
And I don't hate Kate as much as some do [I'd rank her below the Scarlett O'Hara mark on the annoying scale
] but I'm more than willing to separate my admiration for her on aesthetic grounds from Kate's idiocies.
i.e., she'l look hot in pointy ears, methinks.