It sounds poetic to change the word order and say it that way, and since she's a writer it makes sense.

Sometimes titles for shows and movies aren’t really meant to mean anything and don’t follow correct grammar. “Murder, she wrote” doesn’t really mean anything. The way I understood it was that it was just a catchy name for a show about a woman who solves murders.

The main character in the show was a writer of murder mysteries. She wrote about murder. Murder, she wrote.

Olga, it’s a bit confusing, but I guess the meaning is that she wrote the word murder and not a novel called “murder”. Убийство, она написала. Я ухожу, он сказал.

According Wikipedia: The title comes from Murder, She Said, which was the title of a 1961 film adaptation of Agatha Christie's Miss Marple novel 4:50 from Paddington.