OK.
She knows her duties.
Put it on her list to check the fax machine (and any other petty stuff) at least every time she passes by.
Was that her second written warning (plus one oral) about the fax machine paper supply? Third time, they would claim insubordination? Usually a firing would result from someone stealing or damaging company property out of negligence - not petty stuff but if it's a "Right to Work" state, the company can fire you if they just don't want you anymore.
Always show up for work on time, don't duck-out of work early, observe her breaks but always leave -- especially return on time, don't spend time chatting with other employees on work time.
Get her work done and do a good job with a smile (even though she feels like hell).
Sounds as if there is more going on here than we might know. If it is a bad boss, try and get a transfer or another job. If she can't then she is kind of stuck. Is there a union? If so, talk to her union representative and have another person look at the situation for her.
Wish her lots of luck in finding resolution to this employment problem.