The person who had the most positive impact on me would have to be a former girlfriend. She embraced my feminine side wholeheartedly and encouraged me to express myself however I wished to.
Sadly, there were other issues that broke us apart - but we remained friends. She would always say things like "hello, girlfriend" when we met - even when I wasn't at all in femme mode.
My wife's "No talking to EX'es" stance put a stop to that.
Second would have to be the therapist I went to, who helped me understand that all of this (and by extension - me) was OK.