What does the title of My Darling, My Hamburger have to say about the couple's relationship?

The title is a reference to a teacher’s advice on what to do when a guy wants to have sex with you.  This is the situation Liz is in.  The advice does not work.

The title comes from the fact that the book is split into two sections, “My Darling” and “My Hamburger.”  The first section focuses on feelings of love between a couple, and the second one focuses on sex and the consequences.  The second half of the book’s title is ironic, because the hamburger advice does not work.

“What advice did she give for stopping a guy on the make?”

…”You mean about what to do when things get out of control?... Miss Fanzulli’s advice was that you’re supposed to suggest going to get a hamburger.” (ch 1, p. 7)

This advice does not work.  When Liz wants to rebuff her boyfriend Sean’s sexual advances, she suggests that they get a hamburger.  However, they are still in love.  After a particularly bad fight that lasted for weeks because Sean did not get her letter, Liz and Sean do have sex.  She gets pregnant, and ends up having to have an abortion that almost kills her.

The moral of the story is that emotions are more complicated than fast food.  Just avoiding a situation or attempting to diffuse it does not work.  The tension is still there, and so is the passion.  The couple has to learn that you have to have real conversations, not avoidance.  Avoidance results in disaster.