Any society's upper-crust is riddled with immorality, how else d'you think they keep their power? Reputation is king of the public sphere, not private. It is dethroned by public acts.
For Sabina, living in truth, lying neither to ourselves not others, was possible only away from the public: the moment someone keeps an eye on what we do, we involuntarily make allowances for that eye, and nothing we do is truthful. Having a public, keeping a public in mind, means living in lies. Sabina despised literature in which people give away all kinds of intimate secrets about themselves and their friends. A man who loses his privacy loses everything, Sabina thought. And a man who gives it up on his own free will is a monster. That is why Sabina did not suffer in the least from having to keep her love a secret. On the contrary, only by doing so could she live the truth.