By being up at the house with less competition for food, will help her max out. I know sometimes a bunch of yearlings in a pasture can lead to quite a bit of competition for food. If the competition is too fierce, it can lead to less than ideal nutrition.
I bought two horses from a lady who kept two colts and a stud all in one pasture. As you can imagine, the colts were left out. By the time I got them they were emaciated. Of course, this stunted their growth. Now, BlackJack the surviving colt is making a comeback, but it is very slow and it is taking him several years to get to the size he should have been in the first place. Does that make sense?
I think all the special attention your giving her is going to show in the end.
-Kim