By her forgetfulness of what she owes herself.

Then, characteristically, she went on to announce, “If the empress wants me to lay my head upon a block in reward for having placed a crown upon her own, I am quite prepared to die.” It was the kind of flamboyant, exhibitionist remark that Catherine found impossible to tolerate. When Dashkova made certain that her statement was repeated everywhere in Moscow, an exasperated empress wrote to Prince Dashkov and asked him to exercise some authority over his wife. “It is my earnest desire,” she said, “not to be obliged to forget the services of Princess Dashkova, by her forgetfulness of what she owes herself. Remind her of this, my prince, as she gives herself, I understand, the indiscreet liberty of menacing me in her conversation.”

Did Catherine mean she didn't appreciate if Prince Dashkove forgot his duty [to remind of her] when his wife fogot her position. Remind her of this. She gave herself the indsicreet liberty of ...

The expression seems very winding to me. Do ordinary native speakers possibly speak like this style today, though Catherine was an Empress in 18th century? Is it easy for a high school-educated native speaker to understand the English?

Thanks!