I think my T definitely understands me and maybe doesn't "know" me better than I know myself but, like others have said, she can notice patterns and things that I better than I can. She also has the added benefit of talking to a lot of other people with similar problems so I'm sure she notices things I do that her other clients do/have done and it allows her to pick up on it more quickly and understand me better.

I think there is a difference between "knowing" and "understanding" though.