Mother Curie III appears as a hostile feral ghoul reaver if Megaton is blown up after Broken Steel.
Although armed with a .32 pistol, Mother Curie III is an extremely peaceful character, and does not become hostile if you killed Brother Gerard in order to enter the Monastery, or even if you flat out tell her that you're going to wipe out her cult. If threatened, she simply states that she expected some form of religious persecution and that she refuses to respond to violence with violence. If you initiate combat against the Holy Light cult, Curie will simply cower and flee. Her feral ghoul reaver and glowing one followers, however, are not so forgiving and will attack.
"Why... you ARE the Prophet of Atom! I didn't recognize you until now... Your eyes are aglow, your very skin radiates with Atom's Heat! I didn't realize... My Lord, now that you have revealed yourself to me, I do... I see the errors of my ways. Forgive me, for I knew not what I was doing... we will spread your word without the use of the holy water... we will return the Aqua Pura to Megaton. It shall be a test: the worthy will seek us out, and finding us they will find the Message of Atom, drinking the Waters of Light in their souls. Yes! I leave you now, Lord. I can not bear to look upon your shining face any longer."
"Why, to offer Enlightenment to all those who suffer, of course. No more, no less. Atom came to me with a vision: the starving, the ill, the weak, all being made whole and well by receiving the sacrament of Atom's Glow. And so, with our holy water, we can make this vision a reality. When exposed to Atom's supreme Glow, the ill are reborn in his glowing visage. Those reborn never hunger, never suffer, and never age. All our Enlightened brethren need is to know Atom's Glow, and they are happy."