IF it is for self defense, I am not a fan of the 22 but I would much rather someone start out on a 22 they will actually shoot enough to become proficient with and then move up to something more powerful than buy a 40, stick it in the closet, & never shoot it. For that matter, not many thugs are going to hang arround and keep getting shot, even by a 22. On the other hand, a more powerful gun that goes click because the safety is still on or it isn't loaded won't do much to help you.
If it is just for fun, I can't think of a better choice for a new shooter.
Btw, which Ruger? My daughter really liked the SR22 and of course, the Mark series has lots of fans. Personally, I love the M&P 22. Whatever you decide, I would certainly let her handle or shoot a few to see what she likes.
