Have you taken the time to ask her if she needs training on the equipment or help performing her duties? Find out where she is making mistakes and show her how to avoid the problems. I know this will cut into the time you have to perform your duties, but it will speed up the overall speed in the department. This type of solution may even improve your chances for promotion.If she is unwilling to learn how to do the job, she should be removed from the situation. If you are in an At Will state, the boss can fire her without grounds. This might sound harsh, but in the long run, it could be best for all parties involved.
It s heartless, but you work in a business, not in a halfway home.The best wake-up call to her would be a dismissal.Until then, observe and report.