Rocio Pavon-Navarrete pleaded guilty to theft after taking two signed, blank cheques from Brown's home and cashing them in.
The 47-year-old was sentenced to 16 months in prison at Southwark Crown Court, BBC News reports.
The cheques were signed by Brown's manager James Cooper, who stored them at the illusionist's London home for emergencies.
Pavon-Navarrete's 48-year-old co-defendant Bernard Ayanbanjo was found guilty of fraud last month following a trial.
Ayanbanjo paid the cheques - worth £21,550.35 and £11,500 - into his bank account between October and December 2010.
He will be sentenced at Southwark Crown Court next Friday (October 19).