How do I handle a belligerent employee?

I have an employee who often comes in late, and also takes excessive smoke breaks. I have written her up about the lateness, and although she made sure to show up on time for a couple of weeks, she soon went back to coming in late. The other day she took a smoke break after being at work for only an hour, and left her fellow coworker to handle a huge situation all by herself. I reprimanded her for not being responsible She became very argumentative, so instead of arguing I walked away and came back in with a break schedule that allows each employee one scheduled break before lunch and one after. The big problem I am having with this employee is she does not take criticism or disciplinary actions with maturity. She pouts all day long, barely does her job. I can't really fire her, because I need her experience in that department. What should I do?