Final answer:
The most appropriate action for the nurse to take is to review the signs of true labor with the woman.
Step-by-step explanation:
The most appropriate action for the nurse to take in this scenario is to review the signs of true labor with the woman. The woman's complaint of frequent strong contractions that begin in her back and cannot be relieved by walking or changing positions indicates that she may be experiencing true labor contractions. Reviewing the signs of true labor can help confirm if she is indeed in labor and provide her with appropriate guidance.