Crown or Rottenness...

A virtuous woman is a crown to her husband: but she that maketh ashamed is as rottenness in his bones.  Proverbs 30:4

A virtuous woman is a crown - a token of authority - to her husband.  By her virtue (excellent moral ways), she acknowledges his authority to rule, to be head.

In contrast, the woman who maketh ashamed is as rottenness to her husband's bones - a metaphor for weakness, old age, disease.  By her immoral ways, she acknowledges that her husband is not strong enough to rule even his own wife.

A wife's conduct makes manifest the husband's effectiveness in ruling.  Does he rule as a rightful authority or does he cower as a weak, crumbling, old man?