The man invited the neighbor to his home to share his borscht, a soup made of beets and meat stocks originating in Ukraine, but she criticized the soup and poured it into the toilet, the newspaper Komsomolskaya Pravda reported.
The host, whose name was not released, grabbed a kitchen knife and stabbed her in the stomach, police allege.
Investigators told RIA Novosti the man was drunk and when he realized the victim could die he called paramedics.
"I begged her not to die because otherwise they would throw me in jail," the man told police.
The woman died in an ambulance on the way to a hospital, RIA Novosti said.