i'm pretty sure shadowheart's response is something like, "wow, it seems even your father has lost faith in you!", which is just a crazily insensitive thing to say lol. it's the same reaction whether or not she rejected shar, although i don't know if it's different if you romance her?
i do feel like several of the reactions to any version of the durge/orin duel seem inappropriately frivolous i.e. astarion's "twee" comment which really undercut what is meant to be a serious & moving culmination of durge's whole arc, for better or for worse. this isn't the case with any of the companion's stories, which all end beautifully, so it's a shame that durge's arc isn't treated with the same pathos.
Ooof. Yeah
It is insensitive. Really sad that Astarion gets more content AND has the most sensitive and heartbreaking lines.
It does seem more in line with Sharran Shadowheart but not Selunite. Honestly some Shadowheart Act 3 characterization seems like they just thought of Sharran and not Selunite, but that's another discussion, lol.
I did send in feedback for all of the Durge stuff a while ago, and I hope they implement it as well as give all the other companions the same treatment that Astarion got, but if it's not in Patch 8, I don't know if it'll ever be fixed.
They changed the Ansur cutscene and changed companion reactions to a lot of things, so it's not like it's impossible.