That’s an interesting question.
I am not sure what the evidence would be. I don’t know her current origin that well, but what I do know of it, it could happen. In her past origin, her mother made her out of clay and she was given life by the gods, I don’t know where the wiggle room is for her to be trans in that version of the story.
I guess I would have to know where the idea came from, canonically?
I can see the potential of Amazons to be trans but I’m not sure what pieces of information might lead one to think that was the case with Diana. Not saying it’s not there, but I am not aware of the foundation of that theory.