Certainly not robbing her and I agree you have a good setup. As basically said above, choose your specs based on long term technique development and not short term wins. I kept my daughter at 26 inches for over a year playing at national level when I knew 27 would help her compete but also potentially hinder technique.
As for polys - I think while using such a light racket like the PDL, you might stay away from them because with lighter rackets, more shock is sent into the wrist/arm/shoulder and the poly will just add to that. That said, there are some 'softer'/stretchier polys out there now if you were dying to try it you could do a blend.
The flip side is - it is important to also keeping in mind that lighter doesn't always mean better for technique/arms/wrist/shoulder, etc. We've found that groundie and volley technique is more solid with heavier rackets...the lighter rackets can be harder to maintain control/discipline even though you might be able to swing them faster. And also, heavier rackets, with good technique can significantly reduce shock to wrist/arm/shoulder ...but ONLY with good technique. If technique is bad, it's the opposite so don't rush or consider until technique is very good. But if her technique is already great (i.e. she's rarely late, has a great contact point and extension...i.e. letting the racket to the work) then I'd experiment w some weight.
I think our progression was (strung wt):
Age 10: 26, maybe 10oz;
Age 11: 26, approx 11oz;
Age 12: 27, 10.3oz;
Age 13: 27, 11.2oz;
Age 14: 27, 12.2oz;