I worked with NCIS and CGIS quite a bit while I was a SWO. First stop for you and her:
https://www.ncis.navy.mil/Careers/
NCIS is like many other Federal LE organizations and prioritizes veterans and prior-LEOs. That's at least for special agents. Analysts and the rear echelon folks have different requirements and most I've worked with are prior-service with specialties in a particular area. If she has no Navy experience or special expertise, it may not be a good fit. Also, most of the NCIS personnel at many bases are special agents and there are usually only a handful. The larger the base, the more there are, but they're there to do routine investigations and handle other issues. As
@Angry said, they have career requirements that will compete with yours in order for her to advance. As with any military spouse with a professional career, you two will eventually have to choose whose career takes precedence. That will mean you will spend lots of time apart and may not even be stationed together due to her having to hit career wickets to remain viable.
If you are looking for a job she can do that allows her to move with you every time you change duty stations (Nominally every 2 to 3 years), then she should look into working at the CDC (DoD-provided daycare), DoD Schools, or Fleet and Family Services.