The OP's example of Shirley meets that definition.
Exactly.
Physically Shirley IS a woman. Her sex, until the known medical procedures are performed, is still female.
Transvestism is not sufficient to be trans-gender. Women can dress as men and remain acknowledged as women, or identify themselves as women.
For her to be trans-gender she must want to be identified as a man. [Sex is physical and can be changed only through surgery. Gender is defined by identification. It is influenced by behavior, dress, and all the rest. If we cannot agree on this distinction at least, there is no basis for further conversation.]
If she has sex-reassignent surgery, she becomes a male and is properly and unequivocally referred to as "he". In other words, after the surgery he will be trans-sexual but not trans-gender.
Only for as long as she remains physically a woman but desires identification as a man is she transgender.
Now,, she can "self-identify" however she wants.
But the way others identify her is NOT up to her. It is up to them. For precisely the same reason that her self-identification is her business.
So if she wants to be identified as a man, she basically has no choice but to act as a man. By dress, behavior appropriate to the norms of the society she is in, and so on.
If she does so, successfully, then the identification she is granted is the same as her self-identification and she is a successful trans-gender person.
If she fails to do so, she fails as a trans-gendered person. Sad, but true.
Now the main point: proclaiming herself as trans-gender WILL bring about immediate dissonance between self-identification and identification by others, and lead to immediate failure as a trans-gendered individual.