The source states that she will be playing “a leadership role in Nova Corp, the intergalactic space patrol”. The inclusion of the Nova Corps was also signalled by John C. Reilly’s alleged casting as Rhomann Dey, a Nova Corps leader who inducted Richard Rider into the Corps in the original comics.
If this all fits, our guess is that Close could be portraying Worldmind, a guide to the Nova Corps and a keeper of the Nova Force. As such, we may only get a Close’s voice, but it is significant casting nonetheless.
Other cast so far include Chris Pratt as Peter Quill/Star-Lord, Dave Bautista as Drax the Destroyer and Zoe Saldana has been offered Gamora. Ophelia Lovibond, Lee Pace and Michael Rooker are all said to have roles in the space epic.