Williamson County District Attorney John Bradley says Blackburn admitted that she and her son robbed four banks since last December.
Her 35-year prison terms, on each count, will run concurrently.
Charles Blackburn Jr., who is now 17 and was tried as an adult, was sentenced in November to 30 years in prison after being convicted of two counts of aggravated robbery.
Prosecutors say the teen was toting a BB gun during two holdups in January 2008.
His sentences also will run concurrently.
Police say the mother confessed to being the getaway driver.
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