She had two previous convictions for having no insurance and was given a four-year ban in October last year.
MacCourt did have insurance previously but it lapsed because she did not have the necessary documentation furnished on time, her solicitor Valerie Buckley said.
The accused, a single mother, had suffered with a heroin addiction and was now on methadone and getting her life back on track, Ms Buckley said.
She asked the judge not to imprison her client.
Judge McHugh said he had already given the three-month sentence at an earlier court sitting. The case had been adjourned for the accused to get her affairs in order and he confirmed the sentence, as well as a six-year driving ban.
MacCourt was "not above the law", the judge had said earlier.