Greta Steiner is an agent with EUOPS.
In explaining what exactly EUOPS is, something that the chronicler does not explicitly state, we have to go with a couple of statements which describe some but still leaves the organization a bit clandestine, not an unexpected condition for such a mysterious group.
The first brief description I saw is that "EUOPS is the functional actions arm of the European Union and some allied countries that is involved in shaping world affairs to our liking".
The second is that "EUOPS is an organization that does not exist, and if you don't believe it, just ask them. They will tell you EUOPS isn't and it is certainly not involved in directly influencing world events and shaping world affairs to the liking and benefit of the European Union and various other countries using bombs, bullets, assassinations, and bribery".
Would EUOPS be considered by the average person on the street to be on the side of the angels or is it a group that the angels should be in battle with? I would lean firmly on the first side but that Average Joe/Jane might easily go the other direction, especially when some of the activities of the EUOPS agents become known.
The chief EUOPS operative we follow, and there are so many that the chronicler is kind enough to provide useful casts of characters (CoC) at the beginning of each adventure, is Greta Steiner. In her brief bio in the first CoC, she is described as "(Helga Johnson, Colonel Juanita Anderson et al.) - EUOPS assassin. German born, grew up in the old Soviet Union, escaped and became EUOPS assassin and operative after the murder of her parents".
A slightly longer description of her has Steiner being: "Greta Steiner: Born Alexandra Maria Fedrovia, Youngest daughter of Colonel Yuri Fedorova and his wife Angelina Tatiana Fedorova, younger sister of Charlotte Fedorova Yegorov. Born in [East] Germany and grew up in old Soviet Union. She escaped and became a EUOPS operative after the murder of her parents. Worked as an assassin and is also a qualified fixed and rotary wing pilot".
That last part is certainly accurate. In the first pages of the first adventure, she in the disguise of an elderly Russian grandmotherly woman waiting patiently for a plane assassinates an incoming prominent Russian diplomat en route an important U.N. vote. She then drops the disguise and takes on her legitimate cover as a commercial helicopter pilot and flies out of the airport before the alarm is raised.
Steiner, no matter what guise she is using or what name she is going under, is a very dangerous and extremely resourceful weapon the arsenal of EUOPS.
One other sort of really important piece of information about Steiner's personal and professional lives. Both are going to change a whole lot over the course of this series. Not surprisingly, though, Steiner remains a hard-ass not to be messed with.