Bonnie was the name taken by the Zygon leader of Truth or Consequences, a radical Zygon faction which opposed the ceasefire between Humans and Zygons.
After being convinced by the Doctor that it was wrong to consider breaking the ceasefire, Bonnie took the vacant space left by one of the Osgoods, deciding to protect both Zygon and Human races on the planet.
Biography
She originally lived in one of the Zygon colonies, this particular one being located under Clara's block of flats. The Zygons kidnapped Clara, and Bonnie took on her form, pretending to be Clara while she went around England with Jac looking for more clues to the Zygon uprising.
While Bonnie (still in Clara's form) led Jac and some UNIT soldiers into the Zygon colony, she dusted off the Zygon pods in which they were keeping the kidnapped humans. Jac quickly deduced that Bonnie was not actually Clara and that it was the humans that were in the pods. Bonnie ordered her fellow Zygons to kill them.
Later, overlooking the sea, Bonnie prepared to fire a missile launcher at Boat One with the Twelfth Doctor and Osgood inside. The Doctor attempted to reason with her over the phone, but Bonnie, despite the Doctor's protests, fired a missile at the plane. (TV: The Zygon Invasion)
Bonnie records a video of the Zygon Etoine in his true form. (TV: The Zygon Inversion)
Clara, maintaining a live feed to Bonnie from inside a Zygon pod, caused Bonnie to misfire her bazooka, allowing the Doctor and Osgood to escape. Later, Bonnie was able to extract the location of the Osgood Box inside the Black Archive from Clara's mind. After the Doctor convinced Bonnie to not set off the Osgood Box, which was actually empty, Bonnie also assumed Osgood's form and acted as the second protector of Earth alongside the other surviving Osgood. She felt that they were a credit to both humans and Zygons and planned to take on the role of protecting the Earth from threats. (TV: The Zygon Inversion)
Personality
Bonnie was mentally unstable and seemed to suffer from emotional suppression. She often bottled up her feelings, resulting in a calm and cold demeanor but also had an explosive temper. She was smug and sadistic, saying that she was looking forward to hearing Clara scream (TV: The Zygon Inversion) and smiling as she watched her fellow Zygons murder Jac and her soldiers. (TV: The Zygon Invasion) Bonnie seemed to consider murder and war to be a game and was eager to cause bloodshed. (TV: The Zygon Inversion)
However, Bonnie was also childish and when angry, she had a tendency to smash things. Her childishness was also shown when the Doctor pointed out that she didn't actually know what she wanted to do if she took over the world. Having not actually thought that far ahead, Bonnie was unsure how to respond and the Doctor managed to talk her out of starting a war by telling her he forgave her. Bonnie felt remorseful and couldn't understand how the Doctor could forgive her. Feeling she had to try and make up for her crimes, Bonnie became Osgood's "sister" and decided to help her protect the Earth. (TV: The Zygon Inversion)
