I understand the commenters complaint is not that we have not successfully identified a problem with our labor curve, but that if we just assume you can drop this new labor curve into the existing practice structure (that was built on incorrect assumptions of labor progress) we are making a big mistake.
Begin by assessing the situation. What recently happened that may have affected the mother? What has changed? What information did she just receive? Once you understand what the mother may be struggling with, begin reassuring her and encouraging her in the opposite
Many caregivers use the set standard of 1 cm dilation per hour in labor to be the normal course of a labor. If a woman is taking longer than this time she is considered to have a slow labor.