My wife is right in between the two sizes...
My wife is right in between the two sizes so is 23 or 27 going to be better? Utah gets some serious powder so I was thinking 27"
As long as your plans aren't just to walk along packed trails or spring hiking, definitely get the larger version for utah conditions. If you are breaking trail its hard to have snow shoes that are too large in powder.
Take in to consideration whether she will be adding weight (w/ a backpack) and how steep the terrain will be. If you are in the Millcreek area often the shorter is better if you are in the upper regions upper cottonwood and PC open area get her to break trail and go w/ the bigger size.