given your non-reloading status and your 6.5 ammo surplus it would seem 6.5 swede is your best option...also the current over-supply of good quality cheap used swede rifles makes its choice even more appealing....as long as you place your shots well there is nothing wrong with a 6.5 on moose...they penetrate well with proper bullets and deliver just enough energy....moose are not hard to kill like elk....just take your time and place your shot/s well and then WAIT awhile....the old timers used to say wait after the shot as long as it takes to slowly smoke a cigarette....moose seem to take a while to die...if you go after them too fast they can run a long ways...
This is where I would be heading. If she is already comfortable shooting your 6.5 than why change it. Stock up on 6.5x55 ammo and your good for 2 rifles. Never owned a 6.5x55 that didn't shoot well with factory ammo.