IMO the 10/22 is one of the most overrated guns ever sold. I've never shot one that I thought actually shot well. I've never shot a Model 60 that didn't shoot well except for maybe mine now because I think I finally wore out the barrel. It took over 50k rounds to do it though. I've shot that thing a LOT for the past 20 years. I think I finally need a new one. You can bet it will be another Marlin. I might buy a used one that isn't quite as used as mine. Mine still shoots ok but it doesn't shoot like it once did. It still shoots as good as any 10/22 I've ever shot though.
And in my experience I have never had a 60 that could shoot more that 10 rounds without jamming, brand new, well used or anything in between, and I have found everyone of my 10/22's to be just as accurate as the 60's, from my 1967 carbine to my new SS walmart special.
And what substantial investment? 70 bucks for a barrel that will put you way beyond anything a 60 can do? All the free trigger upgrades?
That 1/8 or 1/4 inch of accuracy you gain from a Marlin 60 is a stupid argument, most people do not bench their gun, for most people, especially first gun owners, being able to shoot reliably and being able to hit that pop can is more important.
If it is going to be a target gun then both are out, but a 10/22 would be the far better choice. If a plinker and/or small game rifle then either will work perfect.
Marlin, Savage, or one of the russian imports will be your best bang for the buck, accurate, great prices on the lower end models, still good prices on the mid price model, will give you room for a lot of ammo and possibly some optics. But she might not like any of them, or might fall in love with the ugliest thing on the shelf, worked for me.