How great you have an advocate! Yes, if you feel at all comfortable with and trusting of, your sister, have her go with you. It often takes someone who can see what's really going on to help us on our way. (Who knows, maybe in our depression we take things the wrong way...) No, I personally would not share my journal with anyone new. I might, maybe, write an additional few notes just to take to the T.

Please research anything I suggest before believing...