If I may make a suggestion... if your sister is seriously going to try to hit something with the shotgun... get her a 20ga instead of the .410... if you think she can't handle the recoil (it's hardly any more than a .410), then make sure you buy light 2 3/4" loads. To put a .410 in the hands of a beginner and expect them to hit anything is placing a severe handicap on them... .the pattern is just too small to hit with, except for an expert shot... someone that can center that fast-moving bird in that thin pattern. Get her a 20, and don't act like the kick is any big deal... tell her, "no, it doesn't kick hardly at all... you'll feel a little push, but it doesn't hurt at all"... if she isn't told that it will hurt, then it won't. Once she gets accustomed to shooting the light loads, then you can go up to the heavier ones, if she feels the need.
I think your sister is a lucky girl, to have a big brother that wants to help her get started in a great sport. Just be sure and teach her safety, safety, safety, SAFETY!!! EVERYTHING else comes after that... safety is MOST important.

"Progress, far from consisting in change, depends on retentiveness..those who cannot remember the past are condemned to repeat it." Santayana