Well, problem solved! My son's lovely SO tried it on last night and it's going home with her.
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How did I end up with a dangerous, unwearable skirt in the first place? Because I loved the look so much I thought I would have a professional shorten it properly. And then instead of taking it directly to that professional, I put it back in my closet.
Let that be a lesson to you all. Do or do not, there is no "try".