Have you tested her voice outside of premade .USTs?
- open a new project
- enter in a sequence of "ra"s
- and try that.
next,
- click one of the notes
- press "v" key
- a list of syllables appears.
- choose a VCV syllable
- the note changes to that syllable
- test that.
and I know this is such a stupid stupid question but you have japanese locale, right? (I know, sorry, I know, I'm just rounding out our bases, forgive me ;;orz)