If you want a fun to shoot gun buy the 9MM. If you want to put Bear and or Bad Guys on the ground buy the .40S&W.
I have both and prefer my 9MM for fun but shoot the XD40 a bunch so if I ever need to I can hit something with it.
Well, whenever anyone asks me in person what to get for his/her first gun,
I recommend a .22 because the ammo is cheap and recoil is usually
manageable. Rugers, either revolver or semi-auto, are very good low
cost/high qualilty guns.
On the other hand, I do not recommend a Walther PPK, PPK/s or PPK/S-1 to
anyone who does not have any experience with semi-auto handguns.
These are definately not first timer guns. The caliber is small (.380acp aka
9mm Kurtz) but the guns are so small that recoil is noticable.
So, get her a 22 rim fire and let her shoot the heck out of it. Then let her
move up to a center fire is she wishes.
Good luck, have fun, and be safe!