imma assume you posted this in good faith (in which case you should read my other comment) and explain as best as i can:

non binary and girl aren't mutually exclusive because, among other reasons, non binary is a very large umbrella term (i'm he/they for example, so i could be described as an 'enby guy').

trans and enby are two distinct groups:
you can be trans, you can be enby, and you can be both.
for example i don't consider myself trans because i don't want a different gender than the one i have, i just wanted to do it differently.

as a rule of thumb this whole gender stuff is so loosely defined that it's best to just accept that there will be things you don't get and move on.
the important part isn't understanding someone, it's not treating them like shit when you don't