I am not sure if you are sewing each part, or if you are trying to do all the sections at one time ...
You mentioned the horizontal seam vs vertical ... and, the first thing I thought of was:
I wonder if she is keeping the rows connected as she is working on the sections ...
for example: a nine patch ...
Three rows of squares with three patches in each row ...
working on just one 9-patch:
sew pieces 1 & 2 (in the first row) DO NOT CUT APART
stitch the first two of the next row
stitch the first two of the last row ...
iron them if you must, but DO NOT CUT THEM APART (emphasis <g>)
sew the last patch on each row ... iron them, do not cut them apart ...
now, you have all nine patches together and all the seams will go the way you want.
the next thing I thought was: nine squares sewn together ... turn the patch a quarter turn, and VIOLA! the seams are going the other direction ...
of course <g> that doesn't work with the extra action you have planned in the nine patches - - they are a bit more than 9-patches <wave>