Any episode that prominently features Betty is a lesser episode of "Mad Men." She just isn't as interesting as the show thinks she is, and when she turns up, "Mad Men's" ability to tell stories about bitterness and dissatisfaction becomes noticeably unsubtle.
This week's episode, "Tea Leaves," deals with the passing of time. The constant fear of death and change are both about the fear of being replaced, of the younger honchos taking over as time moves forward.
Henry, Betty's politician husband, to his credit, never once shames her for her changing looks. I can't say the same for "Mad Men" viewers, many of whom appear to see Betty's weight gain as a reason in and of itself to dislike her.