Here's the line of succession as far as I can tell:
1. U.S. Attorney General
2. Deputy Attorney General
3. Associate Attorney General (now vacant)
4. United States Attorney for the Eastern District of Virginia (currently ineligible, since she's only in an acting role right now)
5. United States Attorney for the Northern District of Illinois (Trump appointee John Lausch Jr., sworn in November 2017)
6. United States Attorney for the Western District of Missouri (Timothy Garrison was appointed in January 2018; I'm not sure if he is an interim appointee or if he's been confirmed by the U.S. Senate)
"Rod Rosenweasel’s job has always had Jessica’s name on it. The DC district AG."
According to CNN, "Trump has nominated a slew of prospective federal prosecutors to fill top US attorney seats across the nation, but personally met with one prior to her selection in June" - Jessie K. Liu, who was confirmed by the Senate in June 2017 as United States Attorney for the District of Columbia.
According to WaPo, "The District has no senators who can exercise their prerogative under the “blue slip” process of the Senate Judiciary Committee that requires senators to sign off on nominees for federal district court judges and U.S. attorney offices before they are considered."