Maria Hill is one of the agent of SHIELD, and was nominated by the President after Nick Fury went to AWOL after Secret War. She has possessed excellence marksmanship , agility , weapon mastery.
image sourceOn Civil War, Maria Hill sided with Iron Man to help oversee the Superhuman Registration Act which Captain America rejected it. Source here
As a member of SHIELD in the movie she assists Nick Fury and abide all of commands that would result the best for the SHIELD organization. She also help the Avenger team in many ways and try to coordinate with them in every mission.