And again as you spear to have missed some posts
I have no children and so am unable to answer your question from an actual real life perspective.
But I would think if I did have children my son would, by the time he decided he was a transwoman, if I'd have done my job as a parent well enough, understand no matter how much he wished it was the case he could never actually be a woman.
I'd support my hypothetical son as my child, the child of mine they had always been. I'd still refer to them by the nickname I'd no doubt have given them at some point. I'd also respect his desire to go by a more female name if he wished. I'd support him to live his best life.
I'd hope he wouldn't feel so bad about his existing and only body that he felt the need to cut bits off, add bits and take medication not designed for him that could cause who knows what untold issues in the future.
If he did decide that was what he wanted to do then I'd still love him, I would still support him. I'd sit by his bedside waiting for him to come round, after mutilating his wonderful body that had nothing wrong with it.
But no I wouldn't use she. And i wouldn't have a daughter. I'd use their name, or they when talking about them, and refer to my child rather than my son or my daughter. I'd use their new chosen name, family nicknames etc when talking to them.
And the reason? whilst anyone is entitled to believe anything they want, I'm entitled to believe there are only two sexes, you can't change and my hypothetical male child will always be my male child and I would never allow my own child to believe such a terrible lie as the one which would have him believe he could be a woman.
This is being kind