I thought it was the NCIS REACT Team so I took it to mean that where they were saying they came from was just that branch of NCIS. Plus otherwise wouldn't they be saying their agency too? It also could be that they were all the NCIS ones which was why they were paired together.
This explanation of the real REACT team doesn't say one way or the other about other agency involvement, but it is a branch of NCIS.
Her line was simply that she is from the LA office. She could easily work out of the LA office that we know about without it being an error
. It is implied that there's lots of people who work there, only they're never seen.