Should i report my coworker?

I got my best friend (former best friend now) a job at my work and she's been totally taking advantage of me. We work the overnight shift and she'll come on to work (at 12am) and stay up an hour till 1 then shes asleep till 6am. We work in the health care field so there is definately work to be done during the night. I've had it. She knows she's in the wrong. I've asked her to stop. And I know this is personal politics but I know she dosent do anything all day. If she had a busy and responsible life like had children and/or going to school it would be one thing but she tells me shes lazy and does nothing all day except be a freeloader and lives for free. Shes only in her early 20s. Please help.