You should only validate the valid and never validate the invalid. For instance, as with the example of the cell phone, I agree that privacy should be respected. If keeping your cell phone private is a boundary that you set for yourself, then you must maintain it. But, while you do that, you can help her soothe the underlying fears that cause her to want to inspect it in the first place. The fear is real and valid, that's what you are validating. The accusation that there is something suspicious on your cell is invalid and you don't want to validate that. Does that make sense?
This is where defining and maintaining healthy boundaries for yourself that protect your core beliefs comes into play. We all must establish boundaries in every relationship that we have. If we fail to do so, then the other person involved has the freedom to do whatever he/she wishes to us. We become a doormat and we will not be respected.
A lesson that I learned the hard way is that being right is subjective and requires agreement with point of view. The example of this that I typically give is an argument wherein one person claims the sky is blue. Well, from one perspective, that is a truth; but, from a different perspective it isn't true. One could easily argue that the sky has no color and what is seen as blue is merely light from the Sun being refracted by particles in the atmosphere. Both persons would be correct.
The same types of discussions happen with everyone. To pwBPD, their reality at any particular moment depends greatly on the emotion that he/she is feeling at that time. As a result, the reality that the non is experiencing is vastly different. If the non doesn't listen with empathy to what the pwBPD is saying, the two end up arguing about two completely different things and using different sets of "facts" to bolster their respective positions.
We recently did a poll on this board about the main mistakes that the non makes when trying to deal with their pwBPD and
JADE'ing was the most common. We tend to believe that if we just explain our position, defend what we did, argue about why we did it, or justify what we've done that our pwBPD will magically change his/her mind and see things from our perspectives. In essence, we are asking them to ignore their intense emotions and see things our way (to be empathetic with us) because, after all, we are "right." We ignore their feelings and expect them to see things our way.
One of the most powerful questions that I was asked when dealing with my pwBPD was if I wanted to be right or happy? What that said to me was that I didn't need her to know I was right, I already knew that. What I was really seeking from her was validation of my feelings. That was more than she was able to give when she dysregulated and that was a part of her personality that I just had to learn to accept.