Yes, personal sacrifice is an important part of stoicism. What does blowing the cover even mean? Death? Death isn’t evil, pretty much all stoics are uniform on that point. Stoicism is accepting pain and hardships but to pursue your goal regardless. Musonius had to leave Athens because he didn’t want to shut up about his view points, and the ever admired Socrates who arguably had a large hand in spawning the whole thing died for them. Stoicism is not emotionlessness as we’d define it today, Wikipedia-kun, and has a different idea of what being rational entails too.
And no, she didn’t act on a whim. The whole thing was clearly planned out.