What public lesson was taught to the Comtesse at Lord Greenville's ball?

The Comtesse learns a very important lesson about Marguerite's status, and the fact she has the Prince's favor.

Ah! charming!--charming!" said the Prince, "and now allow me, Comtesse, to introduce you, Lady Blakeney, who honours us with her friendship. You and she will have much to say to one another, I vow. Every compatriot of Lady Blakeney's is doubly welcome for her sake. . .her friends are our friends. . .her enemies, the enemies of England."

Marguerite's blue eyes had twinkled with merriment at this gracious speech from her exalted friend. The Comtesse de Tournay, who lately had so flagrantly insulted her, was here receiving a public lesson, at which Marguerite could not help but rejoice. But the Comtesse, for whom respect of royalty amounted almost to a religion, was too well-schooled in courtly etiquette to show the slightest sign of embarrassment, as the two ladies curtsied ceremoniously to one another.