Incapable of doing the job

We have a coworker who is literally a new CNA; she was certified in June and immediately hired by our hospital. We are not a big hospital by any means, but things do get quite busy at times. We have done everything we can to train her and help her, but it has been to no avail.

She cannot keep up with even the slowest paced day. She disappears during the most critical times of the day, and even when she only has three to four patients assigned to her, she will still manage to only be two of them bathed before lunch.

Her issues go well beyond just working at the pace of 1st shift; 2nd shift has also had issues with her work performance.

Our DON knows that there are issues with her ability to do the work, but it is very difficult to get people who are adequate and available hired (hence why she was hired right out of CNA class). Today, I had to stop my restorative exercises to cover the floor because she managed to find excuses to be in patients' rooms, ignoring call lights and alarms.

I don't know how to approach her about her inability to do her job. She has a terrible attitude and a volatile personality. When we have tried to help her, she has become snotty and rude and made it into a big drama fest. Our DON has spoken to her about her skills but she doesn't seem to listen. I will likely get in trouble for not getting my long term care patients exercised but there were so many things going on and she was nowhere to be found that if I hadn't helped, we would have had more patients at risk of injury and more patient safety issues.

I seriously believe she does not have the wherewithal to do this job. What scares me is that she is in nursing school.