She was a key member of the workhouse staff, she would ring a ball to signal the orphans that it's dinnertime. In the 1968 film when Oliver asks for more food she along with Mr Bumble takes him to see the govorners.
In some adaptations she is romantically involved with Mr Bumble and she bosses him around.
In a subplot involving Oliver's heritage/origins Widow Corney is shown to be something of a schemer. Oliver's mother came to the workhouse destitute and pregnant. She gave birth to Oliver and just before she shortly died, she asked Corney, who was the midwife, to give Oliver her locket. Widow Corney kept the locket and showed it to a mysterious man called Monks, who intented to have Oliver dead due to a possible inheritance scam Monks would benefit from..