Judge Mr Justice Royce said she would serve at least seven years and would not be released unless she proved she was no longer a danger to the public.
During the hearing at Bristol Crown Court, it was revealed that Ms George, 39, became ‘obsessed’ with Colin Blanchard, who she met on Facebook, and that over the internet she sent him at least eight pictures a week of children she cared for at Little Ted’s nursery in Plymouth.
Co-accused Angela Allen, 39, was also given an indeterminate sentence and told she would serve at least five years.
The judge said, ‘This case has caused widespread revulsion and incredulity. It has rocked the city of Plymouth, but the shock waves extend much further, perhaps to every nursery school in the country.
‘You gave parents who entrusted children to your care every reason to believe they would be safe.
How grossly did you abuse their trust. What you did plumbed new depths of depravity.’
The court heard that Ms George had refused to be interviewed by police to confirm the names of the children she abused.
The investigation has centred on 30 children.
Mr Royce said, ‘I find it difficult to accept that she is genuinely not in a position to provide more information than she has.’
Mr Blanchard is to be sentenced at a later date.