Why would you think that I think you're transphobic for telling the truth? I don't. What I also believe is that in any case you should tell the truth, as you see it, in a manner that shows consideration for the woman trapped in a man's body. I'm no medical expert, but I believe that for a biological transition to the opposite sex, it's necessary to start with puberty-blockers at an early age, followed by a sex-change operation at an age where the subject can make a responsible decision, before taking that irreversible step. Transgender women who haven't taken those steps will have to accept that they live in a man's body, and follow your nutritional advice. But the best way to make them accept your advice is by making them feel like you're on their side, that you accept they'd rather be treated like a lady, regardless of the hard biological facts. So, don't lie. Be honest and considerate. That's my amateur advice.