The man - named Shakur - was nearly murdered in the frenzied knife attack, and only survived because he managed to flee the scene, Russian state prosecutor Airat Bikmurzin told the court in Nizhnekamsk.
As the woman stood and faced the judge, Shakur proposed to her in the court, according to a report from NTR-24 TV.
He appealed to the judge for leniency and said they intended to arrange the date of their wedding.
The Russian judge postponed a decision on sentencing until a future hearing, according to reports.
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Mr Bikmurzin said: 'The accused woman failed to fulfil her criminal intention due to circumstances she could hardly influence – the victim managed to escape from the crime scene and found medical help in time', he said.
The man needed three weeks treatment in hospital for stab wounds all over his body, he said.
'Using the knife as a weapon, she stabbed the victim at least 13 times,' he told the court.
He demanded a custodial sentence of up to six years for intentionally causing damage to the health of the man and threatening his life.
The unnamed woman faces up to six years for the nearly-fatal attack. She pleaded guilty to the stabbing incident but denied she had intended to 'kill' her boyfriend and said she was 'drunk' at the time.
It was not clear what the dispute was about.