How do I tell a co-work to do there job?

It's time to sit down with your manager and explain what's happening in detail Your manager needs to know that the work is suffering because of this individual's work ethic. If that doesn't work, as hard as it will be, you have to go over her head and talk to her boss. It is useless having a manager that refuses to do their job and creates chaos in the work place. Your options are very limited. You cannot tell a co-worker of equal rank what they need to do.