In Truly Madly Guilty, Moriarty uses Erika and Clementine’s relationship to explore the complexities of friendship. Although the novel establishes Erika and Clementine as childhood friends, their complicated relationship reveals latent resentment and jealousy. Clementine refuses consider her relationship with Erika as “toxic,” yet she hates the way she feels around Erika:

[T]he intense aggravation she had to work so hard to resist and conceal, the disappointment with herself, because Erika wasn’t evil or cruel or stupid, she was simply annoying, and Clementine’s response to her annoyingness was so completely disproportionate, it embarrassed and confounded her (49).

Erika idolizes Clementine yet feels like a failure: “Self-loathing rose within Erika’s stomach like nausea. She never got it quite right. No matter how hard she tried, she always got it just a tiny bit wrong” (99). These feelings of self-deprecation indicate that Erika has low self-esteem and devalues herself, particularly in comparison to Clementine.

Erika and Clementine’s friendship was not born of shared interests or commonalities. Instead, Pam, Clementine’s mother, saw Erika in the school playground and instructed Clementine to befriend her. Clementine obeyed, unable to deny her mother’s wishes. Clementine hid her growing feelings of resentment as Erika spent more time with her family.