Asma Aweys, 30, was charged with three counts of collecting information likely to be useful to a person committing or preparing an act of terrorism.
Previously Ahmed Aweys, 32, of Redbridge, was charged with three offences of dissemination of terrorist publications, while Abdulaziz Omer Munye, 26, of north London, was charged with one offence under Section 2 of the Terrorism Act 2006.
All three were due before Westminster Magistrates' Court on Friday and will next appear in custody at the Old Bailey on August 31, police said.
The charges come after four people were arrested as part of an ongoing operation by the Met's Counter Terrorism Command.
A 29-year-old man from east London, who was arrested on April 18, remains on police bail.
Additional reporting by Press Association
