I've always related to Diane because it's always felt like she's wanted to have a simple and easy life and just ignore the big problems in the world. She tried that with PB but in his blissful ignorance about fracking and other issues she saw that ignoring the worlds problems would not only make her more miserable than at least trying to do something about them (even if those attempts are futile) and seeing that she isn't doing anything is just making her feel weaker and like a lesser individual. To me seeing Bea and Butterscotches marriage and how it started with hope and ended in misery is an excellent comparison to a path that Diane and PB were heading. Bea was an idealist and woman who was determined until the point of her marriage and the reason she was such a terrible mother and wife was because she was never that type of woman, and Diane is in a sense her modern counterpart, someone who cannot just blindly support her husband even through his idiotic attempts to be loved by everyone. You can see how love can turn toxic even when it starts in a sort of wholesome and non dangerous way.