Speaking to reporters in parliament on Wednesday, Ms Marin said she had not been provided with this guidance. She said she took personal responsibility for the lack of information and again apologised for her actions.
Ms Marin has faced criticism since a gossip magazine published photos of the prime minister attending a Helsinki nightclub with friends on Saturday.
The Seiska magazine said it spoke to witnesses who saw her dancing at the Butchers club, where she stayed until 04:00.
Opposition politicians suggested Ms Marin should have set a good example by isolating voluntarily instead of going clubbing. Mia Laiho, an MP for the National Coalition Party, said Ms Marin had been "irresponsible".
Ms Marin became the world's youngest prime minister when she elected to lead a centre-left coalition with four other parties in 2019.
Finland has fared better than most of its European allies during the Covid pandemic, recording about 196,000 cases and 1,384 deaths.
But since September, infections have been creeping ever higher, with increases of more than 1,000 a day for weeks.
The country has also recorded eight cases of the new Omicron variant, which experts fear may be more transmissible and evade some immunity to Covid.