What Was The True Deciding Factor?
When one looks at the day that both Beth and Diana were having one sees that they were both in the same boat and were experiencing many of the same events. What it all ultimately boiled down to was which one of the women dealt with those same events in a way that could leave her as a survivor.
Both women were having trouble with their children, both had financial troubles (even while working at different socio-economic levels), both ran into car towing situations, both were looking forward to seeing their families at local restaurants later in the day, both had had bad news at the office that day, leaving one fired and the other not getting a promotion, both even; at some point in their lives, became the recipients of unwanted pregnancies. In some ways Beth was actually the luckier of the two women on that particular day in that she avoided getting her car towed, as well as did manage to meet her family for dinner. Hers wasn't necessarily the worse of the two days that the two women were having. When one looks closely at the way that both women dealt with people in their lives one sees that both had a tendency to push others away, Diana even did so with her own children, leaving one of them acting out and the other afraid to approach her mother. Beth actually did better with her child, who was the only person who could put a smile on her face.
Thus Beth in many ways even had it better than Diana.
But Beth didn't deal with chaos in a constructive manner, she had a need to keep creating it. Her actions continually showed that she, as her ex pointed out, needed to be a victim and blame others. Her need to place blame, added to a lack of restraint in creating more chaos, became her undoing. Diana had no such need to create chaos in her life. She blamed nobody for her misfortunes. She knew that she'd made a lot of mistakes and that it was costing her her family.
That difference in the two women's temperaments and approach to life left Diana the ultimate and just survivor.