Board Thread:Theories and Speculation/@comment-25319479-20171101152711/@comment-33156423-20171111181004

Its two nature transformations combined, so maybe she worked on it or Yamato helped her (Ik he's on duty, but who knows, just an assumption), she might have natural stamina or genetics that helped her learn it, and she wasn't important to the Naruto cast back then and was pretty young, but that really doesn't mean she was weak