Bonnie was a rogue Zygon leader who took the form of Clara Oswald. 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)
After agreeing to not detonate the "Osgood Box" that would unmask all Zygons on Earth, Bonnie assumed Osgood's form and acted as the second protector of Earth. She felt that she and Osgood 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)
