She's actually been very quiet! She has her new chair but I believe our boss spoke to her prior to receiving it because she suddenly stopped with the snarky comments and complaining. From the little time I've known her, I doubt she got over her pique after just a few days, so I think she might have been given a talking-to. That's just speculation on my part though.
Either way it's been nice and quiet, both of us have nice chairs, and no one is having back problems.