That's interesting, because I have had the opposite experience. Myshire birds aren't super flighty, but the ones I got from SW are incredibly calm. SW isn't selling hatching eggs anymore, though.
Can you post a picture of her and her home?
I would start by separating her for a day and putting her back in. That sometimes calms a bully down.
Southwest Gamebirds has some good jumbo lines descended from James Marie lines. I have some of their birds and they are big, mellow birds.