She has a .22 marlin with a simple red dot she enjoys shooting
Any .22LR by Marlin is about as accurate (and more importantly, precise) as it ever gets. Can't beat that microgroove system. Good choice.
There's a lot of learning about rifle shooting to be obtained from the .22LR. Cartridges come in long rifle, long (if you can find them), and shorts. The LRs come in many bullet configurations and many velocities. Not to mention birdshot, etc. So should she be inclined, she can experiment for a long, long time with that rifle and the multitude of ammo possibilities. And the cost will be manageable.
And then You could buy and She could mount a Really Good Riflescope (NOT talkin' about a bitty .22 scope with a half-inch tube, fixed-4 power). Maybe something by Vortex or Leupold. Even Bushnell. See how it behaves beyond 75 yards.
Good outdoor weather comin' up. You're off and running.
Enjoy.