I think it's a little erratic, I had it work once but other times it hasn't, if it doesn't easiest thing to do is either oh my ghost or philosophers stone to bring the ghost back, you will have to break them up and remarry as they get set at fiancee when they die which is why it sometimes fails, I guess it's a race between the LTW completing and the relationship state change, then you can just send the ghost back to the netherworld or bring them back to life but it does work that way.