My bet is on this--now that Hedrenatherax is armless and weaponless, Heskara picks up either Fiendbleeder, Dreadskewer, or both (just to be safe--no sense in letting Hedrenatherax get his hands on either one) and slices him to bits. We shall see if it plays out that way of course, but my money is on Heskara in the impending showdown.
Alternatively, she could use Telekinesis to impale Hedranetherax with Dreadskewere and to bring Fiendbleeder to her. That would be a more elegant solution.
There's no chance that Hedrenatherax would let her be a part of his rule after she insulted him, and, although she could escape and join the retinue of another demon-lord, she has a better shot at power here. Hedrenatherax is weakened. She does not appear to be. Two artifact-level weapons are within her grasp. And, if I read the rounds correctly, I think she has an action before Hedrenatherax does.
I think the real question is what will come after the battle. If Heskara wins, she will undoubtedly claim Fiendbleeder and find some way to store Dreadskewer. As a sorceress, however, it's quite possible that she has Mind Blank within her repertoire--and that might well protect her from domination by Fiendbleeder. As a tool rather than a master, Fiendbleeder would be less powerful but more useful... and more treacherous.