I am not sure why the decision is made one way or another sometimes. My DS had 2 - 19's and an 18 in one index and the tester did not want to use the extended norms. I think he might have been more willing if the difference in his score was going to gain entrance into a program. He literally said no based on the fact that my DS already qualified for DYS without the extended norms.
I have not heard of it being used with just a single 19. That said, if the technical report is validiating it being applied in that situation, then you could certainly ask the tester about it. Keep in mind I think she would have to have a perfect raw score in that section to gain 5 points in her scaled scores. I'm not certain, but if I'm reading the report correctly, it appears that way to me. I'm by no means an expert in testing, I only excessively read through the material trying to understand my own kids scores.
Given you already have the experience with DYS, I would look into all of it for her. The worse case scenario is you don't gain anything from it. If you do gain something the payoff for you DD could be huge. Good luck
