Looks to me like she has become a free agent of sorts, disassociated from her coffin. The error isn't on Dismiss exactly, it's on what is supposed to happen first after that --
Sims3.Gameplay.Objects.Environment.Sims3.Gameplay.Objects.Environment.BonehildaCoffin:ReturnBonehildaToCoffin
Have you tried MC resetting the entire lot, I think I suggested TAing her prior (this may not be possible as she isn't a real resident sim exactly) or force deleting her and her broken coffin some other way? How about the old fashioned evict in Edit Town, copy lot, bulldoze, replace, and move everyone back in?