Chuck H and Joe have made some good points that I agree with based on my daughter's experience. I started her on skeet and preserve birds at the age of 14. She was about 5'2 or maybe 5'4" at the most. She tried out many 20 gauge guns but found that the 20 gauge Browning B2000 worked best for her with no modifications. Several years later I got a Beretta 391 20 gauge and because of the shims and two thickneses of recoil pads that came with it the 391 worked even better for her.
The main thing is that youths and small women do not usually have the upper body strength of men the same size and that causes the back arching mentioned above. For this reason having two barels out front rather than one is a problem for them. I have always been a double gun guy but for my wife and daughter a 20 gauge auto with a slim forend like the B2000 or 391 is ideal. A Franchi 48AL would also be good but will have a little more recoil than a gas gun.
Whatever you decide, I hope your lady gets into shooting and enjoys it.
Regards,
Roger
