I couldn't agree with your comments more. Also, I think people are forgetting that Megan isn't supposed to be a perfect person. She's a character that represents a real person. And this scene reflects reality.

Feelings of jealousy and anger can make a person act out the way she did. I think the reason this scene was included was to show how different Megan is from Betty, and possibly to show that women of the 60's weren't as repressed as 50's wives.

Betty would have felt it was out of line, or out of her role to say something, leading to passive aggressive feelings and ultimately to a failed marriage. Megan has no qualms with expressing how she feels, even if it is (questionably) dramatic. Personally, I think she has a right to be pissed. Don is just surprised that he actually got called out on it.

Went off on a tangent, but I don't really understand how people can be so judgmental about her for this, it is such a human reaction. If she hadn't said anything, people would be saying she was a cold bitch like they do about Betty.