The closer you are to them the more they let their perceived mistrust of you show. I think they distrust most people, when in a cycle, but the fact that you're closest to them they feel they have to let you know. The distrust of others I think is also what feeds her social anxiety. No matter how much I told her that my friends like her and people weren't judging her, she never felt comfortable around groups of people. Whether she was there to interact with them or not. It was better at say a zoo than a house party, but a struggle to maintain her confidence in my love in both situations. Like love has some kind of on/off button.