Replying to Girls Skis

This is to help my sister out. She's 16 5'3 and 105 lbs. She really wants to buy the first year of the invaders. She's a begginer/ more of an intermediate skier that only goes in the park occasionally. She's progressing on her current skis. Which are some crappy Alpinas or something like that "not twin tips." 70% all mountain 30% park. Doesn't really do much in the park except for some boxes and a few rails. I know the invaders are a symmetrical ski and should be center mounted.


The question that i have for you is what lenght should she get. Also can she MOUNT these a few centimeters back so the ski is somewhat "more" skiable for her. Is this a good choice for her? Any other skis or comments would be greatly appreciated.

Thanks