Everything about these women stands in opposition. Mrs. Cheveley is flamboyant and theatrical; Lady Chiltern is somber and reserved. Mrs. Cheveley is sexually promiscuous; Lady Chiltern is devoted to one man. Mrs. Cheveley is amoral; Lady Chiltern is all morals. Both are extreme models of women – vice and virtue – that the men in the play find equally threatening. And Lord Goring schools them both, vanquishing both women's former modes of living.
Lady Chiltern's gravity points up Mabel's childlike nature, and vice versa. Mabel is happy living in the now, simply enjoying herself. Goals? Plans? No thanks – as we see in this encounter about Tommy Trafford's insistent proposals:
LADY CHILTERN. […] Robert thinks very highly of Mr. Trafford. He believes he has a brilliant future before him.
MABEL CHILTERN. Oh! I wouldn't marry a man with a future before him for anything under the sun. (2.190-191)
We have to compare these two because (though they don't know it) they are vying for Lord Goring's affections. Neither of them goes in for convention like Lady Chiltern, but they have contrasting natures and approaches to life. Mrs. Cheveley is the artificial hothouse flower in heliotrope; Mabel is the fresh, natural apple blossom. Mrs. Cheveley maneuvers shrewdly to get what she wants; Mabel approaches her one goal (marriage to Lord Goring) with playfulness.
Both dandies of a sort – contrived and deliberately nonconformist – Mrs. Cheveley and Lord Goring handle human beings in very different ways. Mrs. Cheveley uses people, and is unapologetic and public in her dealings. We doubt she has any true friends. Lord Goring works hard for the needs of his friends, at one point even endangering his own happiness in engagement to Mabel. Yet he keeps quiet about his good deeds.
Lord Caversham constantly makes ironic comparisons of these two, leading us to contrast their personalities and actions. Sir Robert is publicly lauded but privately spotted. Lord Goring is publicly irreverent (and irrelevant), but is driven by a need to protect and help others.