My 2 cents worth. While not ideal, a Ruger 10/22 properly maintained/cleaned and fed good HP ammo such as CCI Stingers while not the best HD weapon would certainly be better than only dialing 911.
Short light, replace factory sites with a set of fiber optic sites or red dot type. Cheap easy to practice with, which leads to ability to shoot without fear and make reliable accurate hits. If you have a good 25 round Ruger mag that is lubed and runs cleanly even better. Teaching a novice to use one is very easy, even clearing a failure to fire should it happen. Again wouldn't be my first choice but certainly would hate to meet up with someone who has a loaded Ruger 10/22 at her shoulder and pointed at me.