The regular Weatherby has a 14" LOP the youth 20 is 12 1/2" . To me it is easier to shorten a long stock than lengthen a short one.
I have the Waterfowler 3.0 and I use it when I have to walk in because it is so light. I also hit with it as well as any gun I own.
But, you need to get what FITS her best . The SX3 is a great gun. The best of what she has tried. You can't go wrong there. I have shot a SX2 for over 20 years and it is going strong.
Well, are you gonna pull those pistols or whistle Dixie?