Niki Finley is an agent with the Zealots.
That organization really goes by two names, at least from what we are shown. When we first encounter it, in the second underwater adventure of diving expert Gage Finley and his gifted daughter, Niki, one of the main characters in the drama is told, "right now, we'll just call our organization Rescue ZULU" and that "we are part of an organization that is funded by our government for special operations". The wording there tells us the group is a private sector company whose main, likely only, customer is the U.S. government.
However, it turns out that ZULU is an acronym. In reverse, actually. It stands for "Unfazed, Logical, Unique Zealots". The members are described by one individual as "They're fanatics. Much like me, willing to die for their cause, but funded by your government."
We first meet agents from Rescue ZULU in the second adventure of Finley's father, Gage as he tries to rescue his daughter from kidnappers and is really in over his head. What we learn like he does is that they have been watching the Finley's for some time, evaluating whether either or both would be of use to their organization. This is important because according to one of the agents, that is a routine way of recruitment.
As is shown below, Niki Finley got her 'start' as an important supporting role in the action adventures of her scuba-diving expert father, Gage Finley. She stays an integral part of those tales for all of them but does branch out into her own adventures part way through as she becomes a full-time operative with the Zealots.
One very important aspect to the adventures of young Niki is that she is very good at what she is asked to do for Zulu but she is nevertheless still young and still learning. She will, and does, make mistakes and she and others will have to deal with them.