Replying to Logistics of a CAST setup for the girlfriend?

My girlfriend has been wanting to get into backcountry skiing for a while now, and with Christmas comin up it's seemed like prime time to look into getting her sorted on her first setup. My original scheme was to try and track down something cheap (~$250) on marketplace but so far nothing has turned up.

This is where the newest plot comes into play; my roommate has a CAST 1.0 setup that he'd sell me for ~$200, then I asked a couple of her friends and they'd split getting skins for her so we could convert her current alpine setup (166cm K2 Mindbender 99TI's) to a hybrid one.

Anyone have any input or experience w/ touring on Mindbenders? She's super fit, but wouldn't want to sour the backcountry experience with too-heavy of a setup. Also, 99 underfoot for a backcountry ski? I'm on 112's which feel perfect for me but she's shorter and lighter so may workout fine.

Thoughts and opinions would be appreciated.