I too just found this case today, and have read all of the previous posts. I have nothing of value to add really, other than to back up another smoker's thought that a smoker isn't going to voluntarily go far without their cigarettes. I haven't smoked for years now, thankfully, but smoked for a good portion of my adult life, and would never be outside without my smokes. Many people, yes, even smokers, do not like everything in the house smelling like smoke, and especially if there is carpet or fabric upholstery in the home, or if it is relatively small quarters, as an RV would be, I would think that she may step outside to smoke, especially if her husband happens to not be a smoker. So a smoker is usually going to take their cigarettes if they are going outside for any length of time at all, imo.
The husband talked about her depression. Was she currently on any meds for depression, that we know of? I think if she left voluntarily, she either intended self-harm very soon after leaving, and not to be morbid, but I would think she would want the cliche' 'one last cigarette', and it seems she would have been found close to their RV by now, and the other thought is that she had some sort of mental break, and may have just walked away, with no thought or plan at all. The other possibility is that she met harm at someone else's hands...
I do hope that she will be found safely, but I do not have a good feeling about this. JMO