Can't go wrong with a Marlin 60...I have one...as do most of my friends.
If your SIL likes to tinker though, there are 1001 accessories one could buy for the Ruger 10/22.
The dog is a gentleman, I want to go to his Heaven not man's.--Mark Twain
If dogs don't go to Heaven, then when I die I want to go where they went.--Will Rogers
The more I learn about people, the more I like my dog.--Mark Twain