It turns out despite the fact that it’s being reported as fact in various quarters that it’s just plain rumor and nothing more. We confirmed with Summit that Luisana Lopilato in not invovled in Eclipse.Read more here.
Putting the Kibosh on Rumors: Tanya is NOT in Eclipse
Twilight Lexicon confirms that a recent Argentinian website incorrectly reported that Luisana Lopilato was cast in Eclipse as Tanya. In fact, Tanya doesn't appear in Eclipse: