Why do you want a pump? I wouldn't recommend one for a small-frame woman or girl. Most small women (and even some larger ones) don't have the arm strength to work a pump effectively, especially when swaddled in goose-hunting clothes. My recommendation would be a gas-operated autoloader, which cuts down recoil noticeably by stretching it out over a few more milliseconds. Get the shortest-barrel model you can find, then cut the butt down to fit her. The average factory shotgun has a length of pull (distance from the middle of the recoil pad to the trigger) of 14 inches, designed to fit the average 5-foot 10-inch American male. The rule of thumb is to cut off 1/8 inch for each inch of height under 5-foot-10, so if your niece is 5-foot-2, she needs a 13-inch length of pull. Have the gunsmith who does the work fit on a Pachmayr Decelerator, the softest recoil pad on the market. (Is she still growing? If so, I'd buy an extra buttstock for when she grows up.) The shotgun should be chambered for the 3-inch 12-gauge, not the 20, because you can buy 12-gauge shells that recoil just as lightly as 20s (especially in an autoloader) and kill geese much more effectively. If you're trying to save money, even steel-shot 3-inch ammo doesn't kick all that hard, because the steel payload is lighter than other kinds of nontoxic shot. With steel, BBs are the best goose shot at normal ranges. If you can spend a little more money, buy some Bismuth or Federal Tungsten Steel with No. 2 shot, or Remington Hevi-Shot in No. 4. Even 2 3/4-inch shells will work with any of these. Have her practice with the lightest lead-shot loads that will function in the gun, and she'll never notice the extra recoil when she's actually hunting.