I got to ride one up at west yellowstone, granted we didn't have any powder at all. I ride a cat and my husband has a 2010 m8 so I of course was compairing the pro ride to cat. They had about 1/2 2010's and 1/2 2011's to ride so we switched out and rode both.
On the trails they rode about the same, smoother then the cats to be sure. The 2010 acutally felt a bit peppier on the throttle then the 2011, but both seemed doggy compaired to the 2010 m8.
We rode for a bit on a really hard packed hill, did some drags up it. The 2011 didn't really blow the 2010 away like I had though it might. Just depended on the rider and what line you took but most of the time the 2010 was right on the heels of the pro ride.
What I liked- smooth throttle/power (the m8 takes off with a bang), nice ride on the trails, couldn't tell much else without more snow.
What I didn't like- the handle bars and the pull rope. The bars were too tall (I have a 2 inch riser on my cat) and it almost felt like the bars were too short (width wise), I just couldn't get any leverage on it on uphill turns, it would rather toss me off the downhill side.
The pull rope was made for tall people, I had to stand almost on the bumper to start it. Polaris will preach that the pro only takes one pull to start but you have to pull the cord all the way until it stops or it won't start. When your 5'4" that doesnt work so well.
Other then that, it was fun but I would like to try it in the powder. My advice would be to let her try it and see what she likes.