Susan Phillips said she thanked Beverley Allitt for saving the life of her surviving twin, Katie, and asked her to be the child's godmother - an invitation which Ms Allitt accepted.
'She seemed very competent, in control, and I trusted her,' Mrs Phillips said at Nottingham Crown Court.
The court has been told that Katie was admitted to Grantham and Kesteven General Hospital purely for observation after her twin, Becky, died mysteriously at the age of nine weeks.
At that time there was nothing wrong with Katie. But she was severely brain-damaged when she was finally discharged.
Ms Allitt, 24, from Corby Glen, near Grantham, Lincolnshire, denies murdering four children in her care in 1991. She also denies attempting to murder nine other child patients, the 15-year-old brother of her flatmate and a 79- year-old woman, and denies 11 alternative charges of causing grievous bodily harm with intent to the same people.
Mrs Phillips said that after the twins were born in January 1991 they were admitted to the Grantham hospital with suspected acute gastroenteritis.
Becky was readmitted on 1 April of that year because of vomiting and diarrhoea. It was felt her milk feed might have been making her sick and Mrs Phillips was asked to take some to the hospital for testing.
When Becky was discharged three days later, the milk was returned to Mrs Phillips and was fed to Becky that same evening.
Later, Mrs Phillips said, Becky began crying and screaming and in the early hours of the next morning she stopped breathing. Attempts to revive her at the hospital failed.
The trial continues today.Reuse content