The Question and Answer section for The Girl on the Train is a great resource to ask questions, find answers, and discuss the novel.
I see no evidence of any sort of political symbol in the novel, although, knowing where to look would be helpful. Did your question include a section or page numbers?
You can find the text in question on Page 2 of the Front Matter, two pages past the dedication page. The sections you've references can also be found on Page 58.
Tom and Rachel divorced after Rachel grew depressed by their infertility and he began cheating on her with Anna.