Dorothy Catalonia is considered the antithesis of Relena Peacecraft; whereas Relena advocates total pacifism without fighting, Dorothy strongly believes in human confrontation and conflicts in order to achieve such a goal. She also believes that human conflict will always be a part of life.
However, in reality, Dorothy is putting up her facade of a strong woman, while she's actually insecure, lonely and traumatized by the horrors of war, and she'd stop at nothing to put an end to the carnage.
Dorothy attended the school in the Sanc Kingdom, where Relena Peacecraft was teaching women total pacifism, in the name of her biological and adoptive father. However, she was really a spy for the Romefeller Foundation as her grandfather was Duke Dermail. Though Relena's aide-de-camp expressed doubts about Dorothy, but Relena was confident that she would accept her ideals in time.
When OZ attacks the Sanc Kingdom a second time, Dorothy revealed to Relena that she is a spy for Roemfeller. Though Relena stood true to her ideals, Dorothy told her that peace with pacifism is just a dream. To protect the people, Relena surrendered to Romefeller and became Queen of the World, a figurehead for the Foundation. However, she had tremendous influence over Dermail, and called to the nations of the world to disarm in order to achieve true peace. This infuriated Dermail, who desired military force to maintain peace. Dorothy subtly manipulated her grandfather into going into space to handle the White Fang uprising, thus allowing no opposition for Relena to convince the Earth of her beliefs. However, she could not anticipate White Fang attacking her grandfather's convoy. She then refused to cry and instead honor her grandfather as a great man.
Dorothy soon headed out into space, to join White Fang leader Zechs Merquise, going by his real name Milliardo Peacecraft. At first, Milliardo's first thought was to destroy her shuttle, as she was from Romefeller, but relents when she passionately details his history. She becomes his second in command, witness to him using Libra's main cannon to attack Earth and when Relena attempts to dissuade her brother from his goals. Dorothy later offered Relena gun to shoot her brother but she still clung to her ideals. Therefore, Dorothy locked her in her room.
Milliardo later showed Dorothy the ZERO system, a complex program that could allow humans to anticipate attacks, thus creating the ultimate weapon. Dorothy used the system to remotely control White Fang's mobile dolls into attacking the Gundams, attempting to isolate each one before destroying them. But soon the Gundams began working as efficient as the dolls, perplexing Dorothy. A clash of two ZERO systems caused her to realize that the other coordinator is Quatre Raberba Winner, who had a ZERO system on his Gundam. She then ordered Libras cannon to be fired, barely avoided by Peacemillion.
Soon enough, the World Nation's military, mainly composed of piloted Leo suits, were speared on to intercept Libra, lead by Treize Khushrenada, who challenged Milliardo to a duel. Dorothy wholeheartedly expected Milliardo to accept but he instead refused, stating that he's no longer a soldier of OZ; Treize had expected this. Quinze then pulled a gun on Dorothy because of her insubordination. He then fired Libra's cannon again, wiping out a portion of Treize's forces, though Treize was pushed out of the way by Lady Une/Wing Gundam.
Battle between White Fang and OZ then begun. The Gundams, though not allied with Treize, were determined to stop White Fang from completing Operation Meteor. Dorothy came face-to-face with Quatre, challenging him to a fencing duel. As they fight, though Dorothy claims to love warfare, she deeply hates it for taking her father's life, and puts on a strong face to the world. She then is able to wound Quatre. However, Trowa intervenes. Dorothy then leaves Libra, as it falls to Earth but it is destroyed by Wing Zero.
After the Earth Sphere Unified Nation is formed, Dorothy and Lucrezia Noin pay their respects to Milliardo's grave, who had seemingly sacrificed himself to destroy Libra. However, the latter believes that he had survived.
When Relena calls out to the people stand up against the Mariemaia Army, Dorothy appeared before the crowd watching the big TV screen. She taunted them as dogs wagging their tails and go to their master. The people then realize that peace doesn't come easy for them and that they have to earn it. Dorothy decided to help them in their moment of courage by providing trucks for transportation to Brussels, the Earth Sphere Unified Nation capital, where the Preventers and Gundams were fighting the Mariemaia Army. There, the people, in a pacifist way, stood up against those who think to conquer them. Eventually, it led to complete peace in the Earth Sphere.
Dorothy makes a cameo appearance in the Preventer 5 storyline featured in the Episode Zero manga. The manga also reveals in Relena's story that her father General Catalonia was the original leader of OZ who preceded Treize Khushrenada and was killed around the time of A.C. 193 which in the timeline as shown in the manga is when Trieze took control of OZ.
In M.C. 0022, Dorothy T. Catalonia is the President of the Earth Sphere Unified Nation. She personally gives Preventer agent Kathy Po the orders and data necessary to enact Operation Mythos. When Kathy views Treize Khushrenada's personal history in order to take part in the Operation, she observes a 5 year old Dorothy with her father, OZ leader General Chilias Catalonia. She notes Dorothy is a charmer and speaks similarly even then to how she does in the series, exhibiting an already high level of intelligence. She seems to have been enamored with Treize as a child, wanting to "marry" him.
Skills & Abilities
Though not much is known about Dorothy, from the anime series it is seen that she is a great orator, able to convey her ideas and thoughts to others. Being a spy for the Romefeller Foundation, she knows a few things about being an observer. When Zechs gives Dorothy the ZERO System to control the Virgo II mobile dolls, her skills as a tactician increase significantly, able to fend off the Gundam Pilots.