Of course white women are a subset of women (because not all women are white).
Black women are a subset of women (because not all women are black).
Asian women are a subset of women (because not all women are Asian).
Curly-haired women are a subset of women (because not all women have curly hair).
Women with degrees are a subset of women (because not all women have degrees).
However, all of the above are women because they are adult human females. We can break that down further:
A junior human female is a girl, so not a 'woman'.
A non-human adult female might be a ewe or a doe or a hen or something else, depending on the non-animal species involved, so not a 'woman'.
An adult human male is a man so not a 'woman'.
Girls are not a subset of women (because they are not adult) but they are a subset of 'females'.
Transwomen are adult and human but not female. (If they were female, they would not be trans.) Therefore, transwomen are not a subset of women.
Transmen on the other hand are adult, human and female and so are a subset of women.
These statements are not racist or transphobic, they are just biological facts.