Board Thread:Naruto News/@comment-12509038-20150223214650/@comment-17623-20150225124859

Mecha Naruto wrote: There is also another reason, may be she was introduced in the series to just show the powers of Rinne Sharingan which Madara can't show because he'll use Rinnegan.

Which means she was still hamfisted in because they can't beat Madara, because Madara had the Rinnesharingan as well.