Jacqueline Symcox admitted posting 130 letters to her then partner, and other inmates on his wing, between February and July, in 2019, said prosecutor Gregor Purcell.
But prison staff became suspicious of the amount of mail her partner was receiving and intercepted the letters.
A sample test of 24 sheets of paper from six letters revealed they contained £9,500 of the class B drug. The drugs that Symcox posted could have fetched between £130,000 and £234,000, depending on the current prices in prison.
Police raided her home in July 2019 and uncovered matching stationary, as well as practice drafts of legal letters.
Symcox had also adapted a stamping device to mark the mail as legally privileged correspondence, Mr Purcell said.
Nottingham Crown Court heard £10,000 was transferred into her account, and she had been trying to pay off a £5,000 debt.
Steven Gosnell, mitigating, said she was of previous good character and entered a guilty plea in December 2020. But there had been “significant delays” which were not her fault.
She made full and frank admissions when she was interviewed, he said, but had waited two-and-a-half years to be sentenced.
She regrets what she has done, Mr Gosnell said, and there has been no further offending.
He told the court: “She has stayed out of trouble and stayed true to her true character.”
He said Symcox suffers from a variety of mental disorders, and at the time of the offence was "very vulnerable". She "would find incarceration very difficult," he added.
The court heard a psychiatric report suggested that "she would have been more persuadable and more vulnerable to persuasion."
Symcox, 37, of Tideswell Court, Mansfield, admitted supplying a psychoactive substance.
Recorder Paul Mann QC told her: "You were part of a commercial operation, even though you may not have been at the driving-force end of it.”
On Thursday he sentenced her to 15 months, suspended for two years, with 25 rehabilitation activity days.