So far I've taught her to shoot pistol and rifle, however you are all bringing up some very good points about having a pro teach the shotgunning. We are on a budget, But I can see her getting a lot more out of a few sessions with a pro than me, and she'll at least listen to what he has to say.
I don't want her to get discouraged, as she enjoys rifle and pistol shooting, and had a blast shooting shotguns last christmas when we went home for the holidays (that was when she was using my dads 1100, which did not even come close to fitting her).
The only way I could make it work by taking her shopping would be to not ever let her see the price. My logic with the 1100 with a youth model stock is that the youth model 870 I gave her a year ago (it was my first gun, when I was 12) comes very close to being what I interpret as a great fit.
Everyone has some very good points to ponder, now I am kicking myself for seeing that youth model 1100 LT20 on gunsamerica, seems like too good a deal to pass up, unless it doesn't actually work for her, in which case I'll have a very small shotgun that doesn't fit anyone.