KT may hate Jedi (why the hell did they ever let her write anything but those Republic Commando books? it boggles the mind), but I recall in some interview they did with her that said she actually really liked Mara (presumably moreso before she became a Jedi), and had a hard time writing the scene. And even though it may have made sense, the fact of the matter is likely that had she not taken unilateral action in not checking with Zahn (which any author with any sense would do), it would not have been approved.
And I don't think anything should be retroactively changed, but I'm sure they could magic up some kind of explanation for a resurrection - they have brought people back from basically force-ghost-status before, just not very much lately. Cloning is right out, but I'm sure there could be some sort of way to do it that isn't totally stupid.
And hey, it's only been a handful of years. SW has done weirder things than let presumably-dead characters come back in that span of time.
KT should have talked to Zahn before writting anything. Hell, I wish she stuck with just the RC novels. Maybe the wuthors can put their collective creative minds together and figure out an epic way to bring Mara back. She deserves nothing less because she is an epic character. I would love it if she were still alive. I just don't want her return to be lame like her death. KT should have left that to Zahn himself.