I guess there's nothing to it but to try it, but I know I wouldn't. I have a bunch of Comfortec Benelli's, looking at them now, I don't think I'd believe it could be cut down and still work out properly. Not to mention, that's about a $200 mistake if it doesn't work. Let alone when she grows up and might need a full length stock again (my wife is 5'3" and shoots 2 full length pull Benelli Comfortec's). You should be able to adjust the Comfortec stock shims inside to fit a lefty just fine (it worked for me, I shoot some of my shotguns left handed).

I'd go aftermarket for a different stock rather than cutting down the factory one.