I think your questioning now and thinking and questioning in the dream sort of mirror each other. I don't think your dream was necessarily about sexual preference but more, with your friend, that you needed someone "like" you to express yourself to, like talking to yourself? Some dream interpreters believe we are everyone in our dream, since they are our dreams we are making up from our thoughts and feelings and issues. Having a best friend in my dream would just feel like I was more with "myself" and I would realize I needed to do the self-questioning you are doing (but not necessarily about sexual preference for yourself, maybe how you feel about others?).