Twenty-two firefighters battled the blaze near Church and Maple. Jeffrey Galm, an assistant fire chief with Milan, said about 45 firefighters were on the scene.
Heavy smoke prevented crews from seeing the house when they first arrived.
Authorities said the home was almost destroyed.
"Flames were already breaking through the roof over a garage that was converted to a living space", Rutledge said.
She was taken to the hospital in extremely critical condition with life-threatening injuries, officials say. One was discovered alive and one was deceased.
The fire was reported by a neighbor who heard what sounded like an explosion and saw flames.
Crews remained on the scene for several hours to ensure the fire was out.
The body was turned over to the Medical Examiner's Office for positive identification and cause of death determination.
The victim's identity has not yet been released.