Joanna Maplethorpe, 22, gave the tablet to her friend Alexandra Thomas on her 21st birthday.
The two women had arranged to meet at a nightclub, where Thomas drank several gin and tonics as well as glasses of champagne during her birthday celebrations.
The day before, Maplethorpe had promised to buy her an ecstasy tablet as a present, and Ms Thomas took it.
But the celebrations took a near-fatal turn when, combined with the effects of alcohol, the tablet caused her to suffer a fit. She was rushed to hospital, suffering severe convulsions, as the the effects of the drug kicked in.
At one stage she had to be held down by six members of staff.
It was later discovered that Thomas was more than two times over the drink drive limit and had ecstasy and amphetamine in her bloodstream. She has since made a full recovery.
Sentencing Maplethorpe yesterday at Guildford Crown Court, Judge Geoffrey Mercer said that her crime was at the "lower end of the scale" but added that supplying ecstasy had to be punished severely.
Maplethorpe, dressed in a smart pin-striped blue suit, looked stunned and on the verge of tears as she was led away from the dock while her family watched.
The court was told that both Maplethorpe and Ms Thomas had taken ecstasy and amphetamine - speed - on several occasions before, but had never suffered any adverse effects.
Speaking after the trial, Ms Thomas said she was "absolutely horrified" about her former friend's sentence.
"I do not think she should have got nine months. If it was not her it would have been someone else.
"The police should be going after the main dealers who are selling heroin and cocaine at a profit. I feel really sorry for her - she is only 22."
The pair have not spoken since the incident, under police instruction, but Ms Thomas said she bore her friend no grudges.
"She was my best friend and I am absolutely gutted by the sentence."
Matthew Pascall, defending Maplethorpe - who admitted one charge of supplying a class A drug and another charge of possessing a class B drug, cannabis - said his client felt "genuine remorse" for what had happened.
He said she had been suffering from depression since the incident.