She didn't act unilaterally. I've read extensively on the writing process for the recent multi-author series and it's a team effort. Zahn was not on the team. In addition to initial outlines for the whole series designed by the whole writing team, there are ongoing discussions amongst them as well as editorial and content oversite by both Del Ray and Lucas Arts.
What Travvis has become is the "fall guy" for an unpopular decision. I'm sure RA Salvatore is glad she's come along to become the new whipping person. But by no means did they just get to kill characters on a whim.
Yeah, an unpopular decision that she admitted she came up with on her own, plugged for, and insisted to Lucasfilm that she write, that also fit into her own visible and unpopular biases. She's a "fall guy" like a guilty criminal is a "fall guy" - it was entirely her idea and her decision and her action.
I don't think Lucasfilm/Del Ray cares too much about keeping characters alive, from what I've read there never seems to have ever been much of a debate when they talk about the process of killing characters off, whether it was Chewie, Anakin, or Mara. Lucasfilm just kinda leaves the authors alone, as they know Lucas doesn't really care. The fact they were willing to accept what Traviss was pushing doesn't mean it was worth doing, necessarily.
And I never quite got why so many people hated RA Salvatore - the SW book series as a whole was getting so trite and the characters so unchanging by that point, something had to give. And Chewie was an expendable character at that point.