What might have been done to avoid this situation?

The first step should have been to use an observational pain assessment such as the Abbey scale: http://prc.coh.org/PainNOA/Abbey_Tool.pdf.

This was developed for the person with dementia who cannot speak. This would have shown that Mary has probably been experiencing acute and severe pain and the doctor may have been called sooner. When Mary has been given treatment and medication for pain, the assessment should be continued regularly to make sure the treatment has been effective.