Apparently, the nurse has been diagnosed with Munchausen - a mental illness that makes her dangerous to herself and others. People with Munchausen have murdered their own children and relatives. They are extremely intelligent and manipulative and involve themselves in medical environments and situations any way they can.

Medical schools used to teach doctors and nurses how to identify Munchausen, but things changed. Today, lay people run hospitals, and they have no training, so people with Munchhausen slip in without notice.