The jacket did not fit her well at ALL and that was probably a big part of it. I have wide hips and a much narrower waist (in comparison to the hips), and the hips can sometimes keep a top from going down as far as it should, particularly when I sit down. Then the jacket shoulders go up higher than they should, plus the top underneath it sticks out along the bottom of the jacket. Also the top under the jacket simply may have been longer than the jacket to begin with. Given that that was such an unnatural look/style for her in the first place and she was, no doubt, VERY self-conscious about it, ESPECIALLY with the butt-ugly jailhouse pants, socks and shoes, it's no wonder she was constantly fidgeting with it.
Personally, I HATE wearing suit jackets, and it shows. It's just not my style and they are very uncomfortable. I don't wear suit jackets -- the jackets wear ME.