Work Permit for Confinement Nanny

Hi mummies, I was told that I need to apply work permit for CN. Since I'm only engaging her services for 28 days, I should just indicate 28 days instead of 16 weeks, correct? I mean I might be held liable if anything happens to her after my confinement of 28 days ended. By the way, is a consent letter from the CN compulsory? She worked in Singapore before.