Final answer:
The woman is likely in the transition phase of labor, characterized by full cervical dilation and intense contractions.
Step-by-step explanation:
The woman experiencing irritability, restlessness, nausea, and heavier show, along with the spontaneous rupture of membranes, is most likely in the transition phase of labor. This phase occurs right before the final pushing stage of childbirth. During the transition phase, the cervix fully dilates from 7 to 10 centimeters, and contractions become stronger and more intense.