So, dd is nearly 15.
a couple of years ago she went through a time of questioning, during which she wouldn't talk to us. Finally she told us she was gay. Fine, of course we supported her, and had lots of chats about it, suported her in coming out to the rest of the family etc. No big deal. Relieved that she was chatting about it again, and there were many conversations about stereotypes etc.
She goes to a youth club for LGBT kids and we have fully supported that.
Now she has decided she is non- binary and wants to change her name and pronouns.
Now I don't believe you can change biological sex, and feel that in supporting her to say she is neither, we are saying that a woman cannot be anything she wants to be. She is a women who rejects stereotypes, fine, reject away! But she cannot be neither female nor male, she is female, whether she likes it or not.
I need to support her, and will use her new name
but I cannot work out how to go forward with this.
Bloody mermaids and all they teach, until 10 years ago, she would have just been a 'tomboy' and she could have been who she liked, now we need a label and pronouns and name change etc 
Just not sure how to move forward.
Need support not slagging off