I have two views on this. One is if your daughter in law is as paraniod as you say she is, then probably nothing you do will allow her to bring down those walls. On the other hand, what are the chances of your DIL trusting you? Can you work on that part of the relationship? Usually patients respond to our skill in being very empathic. This does not mean agreeing with them, but rather showing that you understand their situation and how they feel. If you can break some of those walls down, perhaps she may begin to trust you. I always say when in doubt, empathize, empathize, empathize. It does sound like however that these paraniod behaviors are well engrained. Good Luck!