The problem with stringing acoustics left-handed is (except for nylon string classical guitars) the saddle is slanted slightly to compensate for the difference in scale length with different thicknesses of strings.
It always sounds out of tune (because it is). My guess is she doesn't really play this very often and may not be completely sure why she doesn't like it.
On my lefty guitars - I had to do some re-engineering (involved moving the bridge poles by about 1/4 inch) so I could string them right handed without them sounding nasty.
You can get away with straight bridges on classical guitars because the string thickness doesn't vary nearly as much as it does with metal strings.