D..
Please stay out of it between her and her husband. It's one of those "no good deed goes unpunished" type of things.
If a friend bit my head off like she is doing, I'd spend less time with her. I suggest the same for you. She is miserable with all the hormones, etc, but she is being a beotch to you and you shouldn't put up with it. Honestly, allowing it just because she's pregnant is enabling behavior that she may feel free to do to someone else who ISN'T such a "friend" and she may end up getting her clock cleaned. Instead of allowing it, pull back some so that she realizes that her behavior is inappropriate. You don't have to talk about it with her - indeed, I wouldn't. Just don't be so available.
I feel sorry for her husband. I really do.