Williams, 22, was indicted Feb. 22 on one federal count that she used a Crossman Stinger P36 Airsoft BB pistol to try to rob Renasant Bank in Smithville.
The incident occurred Jan. 10.
She will be sentenced in several weeks after the U.S. Probation Service completes a report to guide Chief Judge Michael P. Mills in his decision.
Williams faces up to 25 years in prison and a $250,000 fine.