Mollie originates from Uirō City in Johto, part of the renowned Nurse Joy family dedicated to Pokémon care. Her mother runs the local Pokémon Center, upholding their tradition. Though Mollie enjoyed helping Pokémon there from a young age, she chose to leave, believing she could achieve more by actively seeking out injured wild Pokémon rather than waiting for them at the Center. This pursuit led her to join the traveling airship crew, the Rising Volt Tacklers aboard the Brave Olivine, serving as their doctor and healing specialist for both Pokémon and human injuries.

Typically stoic and serious, Mollie rarely shows overt emotions. She exhibits particular annoyance towards negligence concerning the crew and their Pokémon's health, often frustrated by Friede's occasional forgetfulness about critical communications. Despite her reserved nature, she demonstrates deep care through her medical actions. She avoids dwelling on her past at the Pokémon Center, preferring direct action over waiting. Over time, Mollie forms strong bonds with teammates like Orla and Liko, showing moments of openness, such as discussing personal feelings about family during downtime. Her relationship with former crew member Wy-Yes (Sohdayo) is strained due to his history of giving her false information, causing embarrassment. Yet, she retains underlying care for him, acknowledging some truth in his stories, especially when corroborated by his Wynaut, and actively rescues him from danger when needed.

Throughout her journey with the Rising Volt Tacklers, Mollie participates in key events. She battles adversaries like the Explorers, facing Zirc and his Rhydon, though her Chansey often struggles in direct combat. She provides crucial support, accompanying Liko and Roy into Arboliva’s Forest to investigate a forest fire. There, she aids an injured Paldean Wooper and helps calm a giant Arboliva by expressing shared concern for it. Her medical skills are frequently showcased, diagnosing and treating a stressed Hatenna sensitive to negative emotions, and leading efforts to aid injured Tandemaus revealed as a Maushold family. She also assists in operations like luring a Lapras connected to Lucius and participates in festivals, naturally treating human attendees' injuries.

Following the Rising Volt Tacklers' disbandment after being framed for Laqua’s destruction by Spinel and Exceed, Mollie returns to her hometown a year later. She resumes work at her family’s Pokémon Center alongside her mother and other Nurse Joys, while continuing to venture out to aid wild Pokémon. During this time, she encounters Liko and Roy investigating incidents of Pokémon falling ill near a forest. Mollie reunites with them, and together they discover a Vileplume affected by Laquium, a substance causing aggressive behavior and energy drainage. With Liko, Roy, their Pokémon, and the Rising Volt Tacklers’ Maushold family she brought, they subdue and purify the Vileplume. While expressing a desire to eventually rejoin her former crew aboard the Brave Olivine, Mollie states she must continue supporting her family and local Pokémon for now. Her appearance changes during this period, featuring pink hair in a single left ponytail and an updated dark red and white jacket outfit.

Mollie primarily utilizes one Pokémon, a Chansey, which travels with her constantly. Chansey assists in medical treatments, battles when necessary using moves like Pound, and aids in tasks like handling packages. After the disbandment, Mollie also takes responsibility for the Maushold family previously associated with the Rising Volt Tacklers.