Inspired Nobis sizing for a girl

There are a pair of Inspired Nobis' going cheap on ebay in a 158. I'm thinking of picking up a pair for my sister and keeping them as a surprise for a graduation gift next year, since she will be applying to mountain schools like UVM and MSU. Figure I'd try and get her hooked on the sport like to grabbed me, and what better way to do that than with a pair of Nobis's.

So she is 5'7 or so and probably around the 120 mark. Probably wont get much taller. Think a 158 would be good for her? Shes not a fantastic skier but I've sucked her into the sport enough that where ever she goes, she will be in a position to ski a lot, so growing into the ski wouldnt be a problem.

most likely that'll be fine. I'm tempted to say go for the 168's, but I don't know how stiff those are.

Relatively soft ski. I'd go longer.

price shot up to 300 bucks before the end. She's my sister, but I dont like her that much. I'll keep looking, but thanks for the quick responses guys