Pac Man, I checked the string more carefully and she speculated, “In addition, I sense that my husband would not be thrilled by my shaving (at best he’d accept it), but wouldn’t ever admit it.”
Based upon this, she should consult very carefully with her husband before taking any action.
Fortunately, even if she would take a vow to shave her head every month; her husband will have until sunset on the day he hears about the vow to nullify the vow.
This thread has shone a bright light on the importance of this law of nullifying vows.
No one is allowed to take on unilaterally stringent customs of another community where potential vital interests of their spouse can be affected.