Easter Oregon Mule deer? Maybe an antelope someday?
How about a 6.8spc upper for your Stag. It's really close to
.243 performance out to 300 yds, with a slightly bigger bullet.
Short action. 243, 7mm-08 as several have suggested.
Long action. 25-06, .270. 6mm Remington, 7x57, 257 Roberts.
Don't overlook 6.5x55----it's light on recoil and performs well.
If she can handle the recoil, step up to a 30. .308 or 30-06, either
will get it done on deer and may be a better choice if you decide
to go after Elk.