Should Pregnancy be an excuse for being rude?

As you said, hormones are running wild and even stronger than ever, but at the same time, that doesn't give an excuse to outwardly be rude, especially not directed to only one individual. Perhaps she is using it as an excuse in a way, to justify her actions, knowing that no one would do anything to a woman who's expecting. But it doesn't give her the right to treat people like they're scum, nor acting the way she does.

She still has a mind to use, and if she wanted to she could find a way to better release her problems than attacking fellow workers.

Just don't let her get to you, kill her with kindness so to speak. She's looking for a reason, don't give her one. Focus on doing your job, be polite, and get out of her hair. In a couple months you'll be rid of her.

No, I think "excuse" is the wrong term. When a pregnant person is rude, I think people should keep in mind that they are pregnant and their hormones are possibly acting up, but it should not be completely excused. I have never been pregnant, so I do not know exactly how out of control a pregnant person's attitude is, and even then, it depends on the person. However, I have met enough friendly pregnant people to know that it is possible to be nice when pregnant.You shift manager's negative attitude may be as a result of her pregnancy, but I do not think she should be using her pregnancy as an excuse. She should at least be trying to be nice.

As I said. She is using you as a punching bag and is hiding behind her role as an authority figure and she would absolutely use her pregnancy as a weapon, too.

No, there is no condition that gives anyone the right to be abusive. Ever.