Lake is the novel’s deuteragonist (secondary in importance to the protagonist) and the object of Will’s affection. As the story is told from Will’s perspective, Lake is seen through his lens, providing a counterpart to the previous books in the series, which recount the same events from Lake’s perspective. Although This Girl is told from Will’s perspective, Lake emerges as a round, dynamic character in her own right. Her journey closely mirrors Will’s as she, too, is grappling with the recent death of a parent and is thrust into a new, unfamiliar life as the guardian of a younger sibling after her mother’s death. Lake is characterized by her emotional resilience, sharp wit, and an unwavering loyalty to her family. Her development centers on her struggles navigating immense grief while simultaneously falling into a complicated, forbidden love—a process through which she discovers her own strength and capacity for building a new life from the remnants of her old one.

Despite the tragic circumstances that brought her to Michigan, Lake exhibits resilience and a playful sense of humor. This is immediately apparent in her first meeting with Will, where she playfully pretends to be a zombie to entertain her younger brother, Kel. Her wit and bold personality are constant throughout the narrative, evident in her banter during the “would you rather” game and her defiant performance of the poem “Mean,” where she lists 30 synonyms for “asshole” directed at Will. This ability to find moments of levity and to express her anger with creative fire demonstrates that she is not a passive figure defined by her grief. Instead, she actively engages with her circumstances, using humor and honesty as tools for survival and connection. Her strength lies in her capacity to experience deep sorrow without letting it extinguish her spirit.

Central to Lake’s character is what her mother, Julia, describes as an “indomitable will” (182). She is fiercely honest and direct with her emotions, a quality that often contrasts with Will’s initial reticence. She readily admits to being “in crush” (26) with him and is unafraid to confront him when his actions hurt or confuse her. This emotional transparency is her guiding principle. While this honesty can lead to conflict, it also prevents the misunderstandings that often plague romantic narratives. Her performance of “Schooled,” a deeply personal poem, articulates the lessons she has learned from everyone in her life. In this moment, she takes control of her own narrative, confessing her love for Will and inspiring him to do the same. Her journey underscores vulnerability as the foundation of a meaningful relationship.

Julia, Lake’s mother, is a supporting character whose strength, wisdom, and tragic circumstances shape the narrative and raise the stakes of Will and Lake’s forbidden love story. As a loving and fiercely protective mother, she acts as both a moral compass and a significant obstacle in Will and Lake’s relationship. Julia is defined by her pragmatism and her deep-seated desire to ensure her children’s stability in the face of her terminal cancer diagnosis. Her character is largely static, yet the progression of her illness reveals layers of vulnerability beneath her stoic exterior.

Hoover uses Julia as an external check on the progression of Will and Lake’s relationship. Upon discovering Will is Lake’s teacher, she firmly insists they remain apart, appealing to Will’s sense of duty and his professional future. Her confession that she’s terminally ill to Will and appeal to Will not to compromise her last months with her daughter with a forbidden romance motivates him not to act on his growing feelings for Lake. Ultimately, she gives the couple her blessing, recognizing that their love is a source of strength that will help Lake navigate her future after Julia’s death.

Caulder Cooper and Kel Cohen, the younger brothers of Will and Lake, form an instant bond as soon as they meet. Their connection represents innocence, resilience, and the formation of a new, blended family. As flat but thematically crucial characters, their immediate and easy friendship underscores the natural connection between their older siblings. Their presence is a constant reminder of the responsibilities that ground the central romance. Their quirky personalities, such as Kel’s habit of talking backward and their shared obsession with Halloween costumes, inject moments of humor and lightness into a story otherwise heavy with grief and moral conflict.

The boys’ primary role is to embody the stakes of Will and Lake’s relationship. Their earnest desire to become “brothers of law” (86) underscores the potential for the central romance to heal two fractured families and create a stable, loving home. Caulder and Kel are the silent beneficiaries of the difficult sacrifices Will and Lake must make. Their simple, unconditional acceptance of their new life together provides a stark contrast to the complicated emotional and ethical turmoil experienced by the adults around them.