I totally agree John. In fact that is why I said to let her play what's comfortable to her. That C to G chord progression could also go from C-E-G to B-D-G or as you wrote D-G-B. A lot would depend on the chord following the G. Most musician's have their favorite inversions or shapes (in the case of guitarists).

It wasn't so much noting c(4) as a notation of 1-3-5 more like as a note as to where the frequency range should be centered-- It could be CEG or GCE or even EGC.