The shooting was reported at about 7:30 a.m. in the 1000 block of Connecticut Street, near 25th Street.
Police Lt. Troy Dangerfield said the woman, who is in her 40s, was with a man in the apartment when she was shot by a second man.
He said the woman and the shooter know each other but that the shooting does not appear to be a case of domestic violence.
Police are still investigating the circumstances and the motive.
The woman was taken to a hospital and the shooter was arrested.