Olivia Burgos is due in court Wednesday to see if the plea agreement will be accepted.
Burgos is accused of lying about her reason for buying the firearm in Indiana in 2024.
Investigators say Alphanso Talley used that gun to kill Officer John Bartholomew inside Swedish Hospital last April.
Another officer was critically hurt in the shooting.
On Tuesday, Talley told a judge he'd like to represent himself in his murder trial.