The difference depends on the make/model you're looking at. Some have shorter barrels, some have shorter stocks, some have both. Some of the youth pump shotguns also have an elongated forearm that comes back farther on the receiver, requiring less of a reach to manipulate it.
I recently got a Mossberg 500, bantam. 20 gauge. I'm 5'3"....if I stand up really straight, in heels. It fits me very well, and it also came with a second rubber recoil pad that I could switch out to make it a bit smaller for my son.
I have a 12g Winchester Ranger 120 from my childhood. It is the youth version of the 1200 pump. Why they would make a "youth" 12g is beyond me. Anyway, good gun but no accessories will fit it :-(. I would get a standard model and just let her get used to it. Good luck!!
Check out the Remington youth models in 870 or 1187 Express. The youth model has a shorter length of pull, the distance from the trigger to the end of the recoil pad. This fits smaller women or kids better than a full size shotgun. The 1187 being a semi-auto will weigh a little more, but the extra weight and semi action reduces the recoil. Both of these are in 20 gauge.
I got my 13 year old brother a youth model rossi. I got it in a 20 gauge thinking he would want something with some punch but a 12 gauge in such a light gun would hurt.
Well that gun is SO light that the 20 gauge kicks more than my heavier 12 gauge.
Ok say what you want.....I have heard it all from the guys I go hunting with!!!!
I am 6'-2" tall and picked up one of the 870 youth models a while back and love it for rabbit hunting!!! It has a 21" barrel and a shorter pull....this worked great for tight thick brush while covered in heavy brush busting gear!!!! The shorter pull is awesome with all of those clothes on!!!!
Now back to the point...my wife is 5'-1" and of smaller build and shoots this gun like a champ!!!!
First shotgun was an Ithaca, M-66 SuperSingle, 20 ga. Short reach made it great to handle as a youth. I could hold it properly and it was light enough that I could keep the muzzle up. Generally youth models have a shorter stock and a good one is balanced so the muzzle doesn't droop.
The Remingtin Youth 870 Express with a poly stock has removeble extentions so you can shorten the stock and the barrel is shorter. The youth I am looking at has a 18 inch barrel compared to my 28 inch. The poly stock and the short barrel make for a much lighter gun and easier for youths and those that don't like a heavy gun. I am thinking about getting a 20ga for my 11yr old to learn how to shoot trap. I have 12ga 870 that I really like but it is to long for him. He can hand the recoil but it is not easy for him to shoulder.
If it is for shooting clays i would tell you it doesn't matter then you can always buy a gracoil recoil system and put on it they are a little expensive they run from about 150 to 300 but you can put them on any shotgun may have to do a little bit of trimming but they take out quite a bit of recoil my brother started shooting trap when he was 11 with an 870 comp that we had one put on and that thing shoots like a 22 rifle
The 870 Youth model has a shorter buttstock, is usually on the smaller LW frame (20 gauge).
The newer Micro model has a shorter stock and different forearm for closer reach.
Remington made full size 12's with shorter LOP and called them "youth" models, but that some time back and not commonly seen.