Police Commander Robb Lamoureux says the woman was already in jail in another case Sunday when investigators sent paperwork arresting her for investigation of murder, robbery and theft of vehicle.
Lamoureax says she lived in the same trailer park as Arthur Schroeder and knew him through his grandson.
His body was found Jan. 25. The residence had been ransacked and his pickup truck was taken and set on fire. More arrests are expected as other people are suspected of being involved in killing.
Schroeder was a registered sex offender who spent 18 years in prison for multiple counts of rapes in the 1980s.