Ditto

Rimfire is a great place to start. One great reason is you don't have to scrounge for your brass to reload and ammo cost is another great reason.
The Ruger MK2 is a reasonably priced handgun and you can find plenty of aftermarket goodies. The MK3 is probably good also but I have never handled one.
IF she decides to get rid of the gun the Ruger will hold it's value well if the original purchase price was a good value.