That does seem a bit short.
My kilts are about 14.5-15 in total length, low waist. But I'm 5'2". They're short, but respectable.

But if she's a slender 5'9" she's probably got great stems that can pull off "a belt"

...and if it does end up being too short, she can always wear tights.
opaque tights=magic.

I don't know why this skirt is on backwards, but it's really short, on a size 10 woman, worn with tights, and looks good!

http://www.etsy.com/listing/81877426...facet=handmade