Ann Hamilton, 54, did this despite being warned at the start of the trial not to discuss the case with family and friends. The High Court in Glasgow heard that the next day she revealed to other jurors what she had done and one of them informed the clerk of court.
The trial had to be stopped and the alleged victim, who had already given evidence, will have to do so for a second time in new proceedings.
Judge Lord McEwan told Hamilton: "At the start of the trial I very clearly told all the jury they must not discuss the matter even within their own home. From what has been said to me you heard and understood that and disobeyed it.
"A trial which had lasted for two days effectively hit the buffers. This has caused enormous expense to the public purse."
Lord McEwan after finding Hamilton, who is on benefits and suffers from ill health, in contempt admonished her.