( if anything ancient magic could be declared as rowena's interest given her study, even protective magic given her use and need of it, but so much both offensive and defensive could be used on either side of the coin. magic was often situational.

which means that when geralt hits his question... oh, the directness certainly pulls a little surprise from her, and another time maybe she'd laugh at the idea of lucifer being afraid of her (even though it's true), instead spending a moment mulling over her own answer.

she doesn't know what geralt knows of lucifer or the entire story though she assumes it's enough given dean's need to give people the right details and how long they've been here. though rowena also knows that context is key )

I am the only witch who knows how to return Lucifer to his prison.

( it makes her words specific, calling it what it is rather than its name, and then adding one detail to clarify why that's a feat )

His prison was constructed by God, a cage with a lock that couldn't just be opened. I found a spell that did that... and the one to send him back.

( to lock him back up forever. and whether it worked here didn't matter. she still knew it and he feared that knowledge )