51-year-old Rosa Baca initially told police her live-in boyfriend, 38-year-old Jose Magana, had returned home after being assaulted.
Magana had major injuries all over his body and was transported to a local trauma center where he later was placed on life support.
Detectives say they found inconsistencies in Baca's initial statement after finding evidence in the home.
Baca had assaulted Magna with a hammer and waited hours before seeking medical help, authorities say. They say she also tried to get rid of the evidence.
On Tuesday, Magana died from his injuries and police arrested Baca on several charges including, homicide, assault with a deadly weapon, felony domestic violence and torture.