Question!
Are those two corssed swords in left bottom corner presented in this dialogue?
You cut your screenshots so i cant check.
But if they are, you should be able to attack her at any time during that talking.
Nah, the attack option is not present during the conversation since the party is already in combat with her. Nor can companions be selected during this scene as they're all present for it.
Naturally I could just leave one companion hidden out of combat and then snipe her after I get the reward, but the journal and the story will still treat the events as if I let the Hag go. So I'll just kill her for now without the power and hope they add a dialogue option to kill her later.