At the end of the day, the only really relevant question is what DIN she skis. And the inputs for that are weight, skier type, and boot sole length in millimeters (not boot size). (Height rarely matters.)
Her weight is right on the border between two classes (92-107, 108-125). And I interpret "expert, but not aggressive," as meaning a type II, possibly III. My inclination would be to split the difference -- treat her as a type III if you use the lower weight class, or type II if you use the higher. Either way ends up with the same result.
Assuming that her BSL is in the 271-290mm range, her DIN setting should probably be around 5. That should be within the range of the P12s. You've got the bindings already; I wouldn't worry about it. Personally, I like to keep a pair of 11 or 12 DIN bindings around as backup because I know I can mount them on skis for either my wife or me, even though it's overkill for her.