When virtue and modesty enlighten her charms, the lustre of a beautiful woman is brighter than the stars of heaven, and the influence of her power it is in vain to resist.

The saying praises an ideal of feminine beauty that is intensified—not diminished—by moral qualities. “Virtue and modesty” are presented as a kind of inner illumination that makes outward “charms” shine with a cosmic brilliance (“brighter than the stars of heaven”). The second clause shifts from admiration to social power: such beauty, fused with character, exerts an influence that others “in vain” try to resist. Read critically, the line reflects a tradition (common in later moralizing and courtly literature) that links women’s attractiveness to chastity and decorum, framing moral restraint as the source of irresistible appeal and authority.