I considered myself pretty good at the "is she or isn't she" game having a bit of personal experience in that arena. After spending a work related week in Thailand with our salesman that has been living there for years, I had to throw in the towel. Not many, but most of the "lady boys" he spotted, just had to be upon closer inspection. And these were girls dancing in topless bars. (Please, I was with a sales guy!) Later, out on my own, in a lady-boy bar in an intellectual pursuit, I was in awe.
My guess is if you start really early on hormones, which they do, the results can be fantastic. Plus some natural leanings thanks to Mother Nature can help. Ever since I was kid I was teased about my girlie hips. Even my wife is jealous of them! lol