I don't think Narcissa really believes that Daphne tortures Draco, and Lucius probably doesn't, either, They haven't seen the Pensieve proof of it that they have of Harry's ability to eat magic. So until they do, they can persist in their ignorance, or think Draco is just lying to protect his boyfriend.

Draco would have to figure out that they harmed Harry, first.

Hermione has really grown in this fanfic, and this is my favorite rendition of her that I've written.

And thank you!