To be correct, it is when their identity conflicts with their sexual characteristics.Maybe she is. She never claimed to be trans, which is the point. These are two distinct types of people we're talking about.
An intersex individual isn't trans. Trans is someone who is either male or female, but wants to be the opposite sex.
As I mentioned before, there is significant evidence that there are different ranges of physiological features in brains of men and women and in trans people, many have brains that more closely correspond to their identified gender and brain physiological changes do happen because of genes and their expressions. I am sure that there some cases of trans people where this is not the case and I'm sure there will be some pathologically driven athletes who will live as a different gender just to win but there is experimentally a biological and genetic basis for gender.
But given a choice between demanding expensive tests for women who look too manly and allowing an extremely small number of people to compete in the category of their lived identity, it seems much more efficient and reasonable to take them at their word. I could see examining it further if there were suddenly masses of trans athletes dominating women's sports but that's not the case and instead people are freaking out because some kid won a very low level track competition.