I like the character of Mito, and the back story you gave her really helped with developing that character.
The only thing that as me puzzled is how Mito was able enter the 6-tailed mode. I'm asking because in the manga Tobi had to remove the tailed beasts from the Gedo Mazo and implant them into the former jinchuriki in order for them to have the power of the bijuu.
But other than that a really good chapter as always.