I would tell them that I am fine with how or what they choose, but I would hope I would have talked to them before that moment about a related thing, that concerns me more:

- ... that, no matter how they feel or what they like, that they're clear on the distinction between their body (including their sex) and that it's very important to distinguish between the preferences/feelings and the body parts or norms.
- that it's important to realize that any "late" change will never be perfect, because genetics and/or time will always be against them.
- that it is more important to be able to think freely, and consequently choose freely (e.g. wear whatever you like), instead of trying to change your body.
- and that any changes to make yourself "more beautiful" (as opposed to trying to correct a serious physical defect or handicap) will be a battle that can never be won. You can never be the most beautiful, because there will always be someone better, and if you think you reached the top, you will fight changing qualifiers. It is a futile pursuit. Possibly with examples, as there are plenty of examples, such as of women who aren't at all supermodel-quality but still very much admired. (And that personality counts for a lot more than people like you to believe.)
- and that they should allow themselves to consider and reconsider as much as they need to be certain, to make sure that it is really how they feel as opposed to a spur-of-the-moment or hype or curiosity or confusion.

And then I hope they also understand that your question above falls within this answer and they would understand that the "coming out" is more of an update than anything else.