Shimmer doesn't know anything about Nightshade, but that doesn't mean she isn't interested in hearing about the whole thing. She is very interested in the workings of magic in a general sense, and that's leagues different from anything she's personally experienced. She's sure the courts would enjoy being able to do that, to retcon reality in such a way...

The tech has always been theoretical in most ways, so the forms it takes has shifted around a lot. The primary concept is to change Fae themselves in a way that will no longer be affected by iron, or that will be able to corrupt or change the iron when it comes into contact. Metals can lose their iron effects after being exposed to magic for a long period of time, so the idea is to create an effect like that but a much more rapid pace. Rapid enough that the Fae is never harmed.

She will feel the need to correct him and say that she isn't nice, he only think she is because he hasn't known her long. She was personally responsible for the torture and deaths of many of those changelings the Mother went through, after all.

She's drunk enough that all of that comes out almost casually - just a statement of fact. It's the way things are.