I don't know if this help, but my son, advanced junior player, had wrist issue last year (he was 12). We went through a few racquets and also medical treatments. Finally we got referred to Paul Ness, who is an official trainer for the ATP (if you watched the 2013 AusOpen final he was the trainer who worked on Murray foot blisters) within minutes he figured out what the issue was and gave my sons some exercise and the problem went away. The diag was that my son probably felt down at some stage and hurt his wrist and some specialized physio works was all that needed.
The point I am trying to get across is, if you haven't already, to get her to see a specialized tennis physio/trainer. Given she has good technique it is highly likely she has some injury that may be not caused by tennis.