Hilde was a colony volunteer soldier to the OZ space army. Upon hearing Gundam pilot Duo Maxwell criticizing the colonies for their involvement with OZ, she encouraged the young pilot to become a volunteer too, unaware Duo planned on destroying OZ's Lunar Base. Soon after that, Hilde noticed Duo attempting to sneak aboard a shuttle transporting other colony volunteers to the Lunar Base. Duo escaped the colony after stealing a Leo but Hilde gave chase in one of her own and eventually aided in his capture. Aboard a mobile suit shuttle, she interrogated Duo but upon listening to him, began to question OZ's methods. After the Gundam pilot broke free of his shackles and left the shuttle in his damaged Leo, Hilde again went after him but this time, shot down a Taurus Mobile Doll that was attacking Duo and allowed him to enter the Lunar Base.
Hilde would soon leave OZ after this to live in an L2 colony. Duo joined her eventually and the two lived together on her salvage yard which allowed Duo to gather supplies for his incomplete Deathscythe Hell. During this time, Hilde brought Duo's Deathscythe Hell to him outside their colony to fight Trant Clark after the OZ officer had tracked Duo down and forced him to test Wing Zero's Zero System. Hilde and Duo continued to live together until the colony rebel organization White Fang began their takeover and attempted to recruit Duo only for him to refuse and leave the colony, concerned for Hilde's safety.
Exactly one month later, Hilde snuck aboard the White Fang-controlled space battleship Libra to steal schematic data for the Gundam pilots. During her self-appointed mission, she met and talked with Relena Peacecraft before escaping in a Taurus. However, the White Fang sent out the rebuilt OZ-13MSX1 Vayeate and OZ-13MSX2 Mercurius mobile dolls (fitted with combat data from Gundam pilots Trowa Barton and Heero Yuy) to pursue her. Duo was able to save her but Hilde suffered a number of injuries and was last seen being wheeled into a medical room in the space battleship Peacemillion.
Hilde is last shown at the end of Endless Waltz, spending time with Duo in their home colony. In the OVA, they work together in a scrapyard; in the movie, they're eating lunch together in a Chinese restaurant.
In MC-0012, Hilde leaves Duo, and he travels to Mars. Some time after that, Hilde follows, becoming a librarian in the Lanigreen Republic. During her time working at the Martian National library, she becomes an expert on nanotechnology. Here, she also reunites with Duo, and he moves in with her. After he proposes to her, the two marry in MC-0015. However, Duo soon leaves again, and when he returns in MC-0016, Hilde has begun to care for the children of a local church orphanage. When the priest of the church leaves it to Hilde and Duo, his debt is also passed to them, with Hilde bearing the load of the debt, and Hilde demands a divorce from Duo. He signs the divorce papers and once again vanishes, but not before promising to help Hilde recover from her debts.
Sometime before Duo returns in MC-0017, his son, Duo Maxwell (II) comes into her care, however it is not clear if he was born to her while Duo was traveling the planet or if he was adopted by the orphanage. Hilde says she thinks him to be a lovechild of one of the father's women, however Duo muses that the child would have been born while he and Hilde were still together. In MC-0017, Father Maxwell brings Naina Peacecraft to the orphanage, placing her in Hilde's care at the request of Zechs Merquise.
While still a nun, Hilde continues researching nanotechnology in a search for a cure for the PPP nanotech on Duo's behalf, and inadvertently discovers a nano-hologram of Zechs Merquise created by the Noinheim Group. This leads to her supposed death in an attack on the orphanage, however she is later shown to have survived. As her divorce never went through, she becomes First Lady of the Mars Federation when Duo Maxwell is elected the 3rd President sometime in MC0023.