Nikita was a renegade teenage girl who got set up by the Section so they could recruit her to help them do their dirty work.
She was framed for a crime she didn't commit. Taken to the Section, trained to be an operative and killer of terrorists.
This was not in her nature, while she was overtly rebellious, she wasn't vicious, ruthless, cold or vindictive. She was just outlandish in dress and actions like many young girls trying to find themselves. Her work at the Section did not come easy for her as she believed in fair play and the safety of innocents, who were deemed expendable as an unfortunate but necessary part of "collateral damage" in the war against terrorism.
Instead, she became a "corruptive" and "bad" influence with her soft side and fair play on Section functionaries like Michael, who has a crush on her and she eventually reciprocates his feelings, along with Section workers Walter and Birkoff, much to the anger of Section head Paul, known in the ranks as Operations, who is always one step away from putting her in abayance (on probation) or outright terminations (which he did once).
Nikita walks the razors edge between stopping terrorism but not with collateral damage. That is a no-no in their world of accidents happen, don't concern yourself with those little problems.