Ms. Brooks’s resignation in July followed closely the News Corporation’s abrupt decision to close News of the World, Britain’s highest-circulation Sunday newspaper, after 168 years of continuous publication.

Ms. Carter, who was described by those who worked with her as Ms. Brooks’s “gatekeeper,” with close knowledge of Ms. Brooks’s schedule, e-mails and meetings, lost her job as personal assistant amid the storm of recriminations after the disclosure that one of those whose cellphones had been hacked was Milly Dowler, a 13-year-old girl who was abducted and murdered in an outer London suburb in 2002.

News International’s acknowledgment that the The News of the World had hacked into the teenager’s phone at a time when there was still hope that she remained alive was a watershed in the scandal. Ms. Carter’s departure from News International closely followed that of Ms. Brooks, but Ms. Carter continued to write a weekly beauty column for The Sun until that, too, was discontinued in December.

One of the issues under investigation by Scotland Yard is whether any documents or e-mails pertinent to the inquiry were deleted or destroyed as part of a cover-up. Although News International has provided investigators with an archive of 300 million e-mails, the company has been accused of having deleted e-mails and of providing former employees with lavish payouts on the condition of their silence. It has also been accused of making selective leaks to other sections of the news media that Scotland Yard suggested constituted a “deliberate campaign to undermine the investigation.”

According to two former staff members who did not want to be named because they were discussing a topic that was the subject of an active police investigation, Ms. Carter was fiercely loyal to Ms. Brooks. A person who claimed to have been present on the day that Ms. Brooks cleared out her office at News International’s headquarters, and who spoke on condition of anonymity, said that the two women were seen carrying items to a parked car.