Constance says, "No; that will ruin us both; temporise; tell the Queen, who is hungry for love, that you love her; and that, as she cannot marry a subject, you will be content with me, whom the Queen loves." Norbert objects, and no wonder, to this lying business, but he does it; and the Queen runs to Constance, crying, "I am loved, thank God! I will throw everything aside and marry him.

I thought he loved you, but he loves me." Then Constance, wavering from truth again, says that the Queen is right.

Norbert does love her.

And this is supposed by some to be a noble self-sacrifice, done in pity for the Queen.

It is much more like jealousy.
Then, finding that all Norbert's future depends on the Queen, she is supposed to sacrifice herself again, this time for Norbert's sake.