Cissnei's page in the Crisis Core Ultimania mentions that she was a special existence within the Turks who was largely unknown to the regular Turks members at the beginning of Crisis Core. It also mentions that Cissnei belonged to a detached/supporting division of Turks that consisted only of members who received special training for the group.
It was revealed in the special Reno episode in Before Crisis, which occurred simultaneously as the intruder incident at the Shinra Building in Chapter 4 of Crisis Core, that Cissnei was assigned to look into the relationship between the security robots malfunctioning and the Shinra building being under attack.
In a conversation between Reno and Rude while being assigned to a smaller and more mundane assignment at the same time the attack and security breakdown were taking place, Reno, while complaining to Rude that Cissnei was getting special treatment (due to his own lack of interest for his current assignment), casually stated that the new recruits do not even know of Cissnei's existence within the Turks, while Rude retorted that Cissnei is careful and diligent when it comes to her work.11
Although it is unknown if Cissnei joined the Turks before, after or at the same time as Reno and Rude, it seems that she is on equal footing with the two more well-known Turks. This is demonstrated in the FMV sequence near the end of Crisis Core, when Cissnei delegated different coordinates for herself, Reno and Rude to search in when they could not locate their targets.
As Reno and Rude's fellow colleague, Cissnei will give them credit where credit is due. When Reno and Rude joined Cissnei in ridding the streets of Sector 8 of malfunctioning security robots and Gensis Copies, she praised Reno for his quick work eliminating the enemies and told him: "That's our Reno, fast as always."12
In turn, Reno and Rude shows care and concern for their young colleague, as well as trust. This was shown when Reno suddenly lost contact with Cissnei after she asked Reno to meet up with Rude while clearing the streets of Sector 8. Rude phoned Reno almost immediately after Reno lost contact with Cissnei. After asking his partner if something happened to Cissnei, he told Reno not to worry about her, and the two of them proceed to finish clearing the west side of Sector 8. When they finally went to look for Cissnei, they found Zack trying to snatch Turks' job (he wanted to rescue Cissnei from the Genesis Copies she was fighting), and complaining to Tseng to do something to help Cissnei, to which Rude told him that there was no need for concern, fully trusting his colleague's ability to handle herself.
Tseng has also shown a lot of trust and faith in Cissnei. When Cissnei was about to board the helicopter to look for Zack and Cloud, Tseng blatantly told her that she is going to be the person that saves Zack's life, fully putting his faith in her.
In a DMW sequence when Cissnei declined Zack's invitation to have dinner together due to being just given an assignment, Zack offered to talk to Cissnei's superiors for her, to which she replied that her supervisor is pretty scary. It is generally believed that the supervisor that Cissnei was talking about is Veld rather than Tseng, as Veld was still the leader of the Turks at that time.