GITS is a little unusual as the movie, manga and series really have nothing to do with each other. The movie is loosely based on the manga and the series is loosely based on the manga and movie. But..neither the movie nor the series get everything completely correct. Like, in the series and movie everyone is always saying how scary the Major is, but we never really know why. But, in the manga, it's very clear that the Major its a major bitch. In the manga, she's always fighting with the chief, and tends to order everyone one around and could care less for her team's safety. Seriously, you get the impression that she wouldn't hesitate to sacrifice her entire team for the sake of the mission. Not someone you want to go against.
She shows a lot more compassion and emotion in the series and movie. Heck, in the series she does a couple things that I can't imagine the manga Major doing. So, it's kinda weird that her personality is so completely different through the three iterations of her. I would highly recommend reading the GITS manga, as well. Both the original and the second Manga have been re-released. And they're unedited for the most part. The Original Japanese manga had a lesbian sex scene with the Major and her friends, but it was later permanently cut 'cause it did really help the story that much.