Oh boy... hate to admit it, but I'm having a problem with this, too.
I have her at level 53 or so, her PROT is 113, her armor boosts that to 177 Defense... and I still don't get the scene with Huan and Shu. I have all 108 stars (I even have all the stupid squirrels and McDohl), no one's died other than Kiba, and I press the response in time (at least, I run forward and go into a fighting stance), and I still can't get the scene. Any ideas on what I'm doing wrong?
One thing I considered was that I may be thinking the scene is earlier than it really is... Huan's supposed to talk to Shu right after he says Nanami died, right? Or do I have the timing wrong?