i agree. you don;t really know until you try a few pairs of differeing lengths. my point was for the OP not to be put off by the ski lengths for his wife when dealing with twin tip powder skis. also since lots of people are buying online without demoinmg, they are less likely to have tried the pair before buying. foolish maybe but it;s what people do.
i bought a pair of 169 K2 PEs online without demoing and everyone told me they were going to be too short. However, I have skied on that length ski and felt most comfortable with it. However, now that i;ve skied on it, I should have taken the advice that they were too short and bought slightly longer.