Why are you worried about body harm? Nothing can be done, if you're talking about operations, until quite some distance in the future!
There's counselling first, to see if that's what she really wants, and then medication to take to change her voice, encourage bust growth, discourage facial hair growth etc before an op will take place, so there's plenty of time for her to definitely make up her mind and for you to get used to the idea!
In the meantime, you could both enjoy shopping trips, Covid permitted, and you can learn together about what she likes and what she expects from you - love and hugs to start with, and understanding as you go on!
You're gaining a granddaughter, and my best wishes for her!!