I Am A Speech Pathologist And I Also Manage A

I am a speech Pathologist and I also manage a therapy department. One of my office assistants, over the past year, has begun having slured speech, making frequent mistakes on routine duties and the biggest issue is I work in an organization that wants to "discipline" her versus listen to my concerns. The biggest issue is that she doesn't appear to have any insight into these errors and when I confront her about them, she has excuses and says the work and environment are "overwhelming". I am very concerned there is something medical going on.