For a time I dated a lovely ladyboy from Pattaya. She was one of the sexiest women I have ever seen. She had everything and something extra. She LOVED to be called in feminine pronouns. I LOVED to call her my girlfriend, particularly when she did particularly un-ladylike things (like pee standing up - true story!).
My most common thing to do has been to remember the end goal. If she's MTF transgender, call her a she! Blimey! It's not rocket science! If he's FTM, call him a HE! Is it so hard?
Much love to all of you who are brave enough to be true to yourselves!