KSP says 49-year-old Donna Gaines had been telling people she had killed her boyfriend, Gregory Keith Sigler of Cromwell in Ohio County.
Troopers say Gaines had been signing and cashing Sigler's monthly checks.
Investigators also determined Gaines killed Sigler at her residence in Cromwell, then burned his body.
They also recovered a rifle which may be the murder weapon, and found trace bone fragments which may be human in a fire pit on Gaines' property.
Gaines is lodge in the Ohio County Detention Center in Hartford, charged with murder and first degree forgery.