Jesus, woke up on the wrong side of the bed much?
Get the larger size just to be safe, and adjust the binding to fit her boot.
Sorry not /thread
No. Don't do that. That's like telling someone to wear thick socks if a pair of boots is too big. I wear a size of boot, that, fits a medium and a large version of a particular binding. Fortunately, a local shop had a large binding and when I put my boot in that supposedly fit the large binding, my boot did not fit. The binding was way too big for a boot size that supposedly fit.