I don't think UO is a juniors store. Its sized in even numbers and fits me like any of my other missy clothes. I wear the same size I usually do. I sense that it's targeted towards college students and 20-somethings, not teens.
I wouldn't get my hopes up about that first dress. I have seen it in person.
First of all, the material is cheap and pills like you can't even imagine. It isn't really a "sweater" dress, more like a sweatshirt dress. It's extremely soft and warm, and I don't generally have high standards about materials, but I didn't like it. Even that I could have overlooked if it fit well, but it didn't.
Shana, you're busty like me, and this dress is never going to work. I don't even bother trying Kimchi and Blue dresses anymore because they always have that damn empire waist and it does not fit over my chest. I had to go up to a medium, and then it just wouldn't fit anywhere else. I don't always have a problem with empire waists, but I definitely did with these dresses (there are several styles like this). They also look unflattering from the side.
As a matter of fact, if you look at the model from the side view, you can see that not only is the dress poofing out in the front, it doesn't even seem to be sitting correctly under her bust, and she is fairly small chested. I think she gets away with it, but you and I definitely would not. My chest more or less fell out of the top before I was able to pull the empire seam down to an appropriate position.