Laura Cunliffe, 23, put black and white cat Mowgli into the microwave for a minute after it attacked her pet goldfish.
Cunliffe said that she realised what she had done and removed the kitten from the microwave, but the damage was already done and it died later.
Her solicitor argued that Cunliffe has suffered with psychotic depression, and had been sectioned under the Mental Health Act 20 times in the past.
Despite this, the judge sentenced Laura Cunliffe to 14 weeks in prison for her crime.
Family members present at the trial shouted: 'She doesn't know what's happening - she hasn't a clue!'
They also claimed the judge should not be sentencing her to prison time.
But Judge Foster told the defendant: 'This was an act of utterly horrendous cruelty on your part on an animal that, as far as I could see, had come to trust and rely on you.'
Cunliffe has also been banned from keeping animals for life and told she cannot have this reviewed for at least five years.
According to her lawyer, Laura 'still can't believe what she's done' but when pressed on whether she knew what she was doing at the time of the incident, admitted that sadly she did.
An RSPCA spokesperson said: 'This was such a sad case and clearly this poor kitten would have suffered terribly over a prolonged period of time. Sentencing is a matter for the court but we hope that this means that other animals will not have to suffer in this way in future.'