Jonathan Baines, 44, also known as "Willy", was found dead at a house on Ropery Road, Gainsborough, on 1 August.
Pamela McLaggan, 51, of Greystones Road, denied murder but pleaded guilty to manslaughter.
Prosecutors accepted her plea. She was remanded in custody at Lincoln Crown Court ahead of sentencing on 21 December.
The court heard Mr Baines had been out for the day at Market Rasen races before returning to Gainsborough and visiting pubs in the town.
A woman has admitted killing her partner who was fatally stabbed after returning home from a day at the races.