Brenda Barattini, 26, allegedly sliced off her 40-yar-old boyfriend's 'manhood' after breaking into his house in the middle of the night.
Police in Argentina arrested the young woman after her bleeding lover staggered to the phone and managed to call emergency services.
He was admitted to hospital with 'sharp cuts to the penis and testicles' and is said to be responding well to treatment.
Trainee architect Barattini pleaded guilty to the assault when questioned by police over the weekend, but remain unsure of her motive.
Barattini was formally charged on Sunday.