Chances are 100% that you will have to bore the cylinders for oversized pistons. Look to Crusinimage for a set of decent ones at lower cost. MAKE SURE the machine shop sets the pistons clearance at 0.0010"-0.0018", NO MORE. If this isn't observed, the bike will both burn oil and will refuse to idle from Day One following the rebuild.
Is your daughter adventurous? The 450 has the most-sudden launch of any smallbore twin I've ever seen. When I had my 2nd one I wanted my wife to take it up: the strong, sudden launch scared her too much, so she never rode it again. Sad, it was gorgeous: her dad bought it from me and rode it for a decade before he bought a Silver Wing.