"...[T}rans women are trans women, that they are people who, having been born male, benefited from the privileges that the world affords men, and that we should not say that the experience of women born female is the same as the experience of trans women."
"Girls are socialized in ways that are harmful to their sense of self – to reduce themselves, to cater to the egos of men, to think of their bodies as repositories of shame. As adult women, many struggle to overcome, to unlearn, much of that social conditioning.
A trans woman is a person born male and a person who, before transitioning, was treated as male by the world. Which means that they experienced the privileges that the world accords men."
Chimamanda Adichie stated the above in a clarification about some problematic things she said recently about trans women, and invoked the girlhood of cis women as a fundamental distinction between trans women and cis women. Chimamanda Adichie is wrong here, but not for the reasons I've seen floating around.
Instead of challenging these points, most critiques I've seen try to shoehorn trans women and their girlhoods into this logic. "Trans women do have authentic girlhoods, and don't have male privilege," they say. Instead of trying to fit trans women into this politic of authenticity, we should be challenging these foundational assumptions.
A definition has to be correct in all cases to be accurate. A single counter example breaks it down, and regarding Adichie's first point, there are tons. However you define "authentic girlhood," it leaves out thousands of CIS women. Not all cis girls have painful/difficult puberty, or bad cramps, or periods at all. Some cis women are born without ovaries or vaginas! With XX or XXY or some other chromosomal situation. With or without breasts. With more or less estrogen/testosterone. With or without body hair... with or without "female socialization." With or without certain types of oppression.
Adichie states that "girls are socialized in ways that are harmful to their sense of self," and gives examples. But not all girls experience this socialization, and not all in the same ways. Some experience them much more than others. All of these girls with all of their diverse experiences are still girls. If the definition of "authentic girlhood" is so rigid that it leaves out thousands of cis women, then it's specious.
Related, but more on her second point, some women have privilege (class, race, ability, etc) and this makes their girlhoods wildly different than other girls'. They're all still girls. A rich white girl likely has a potentially completely different girlhood than a poor non-white girl. They're both still girls. Privilege does not negate identity.
There is so much diversity among experiences of cis womanhood that to try to draw a box around what cis women experience to create an "authentic" experience will always fail. (In fact, there's as much difference among cis women as there is between cis and trans women).
So where do you draw the line around "woman?" If you're drawing around "authentic" girlhood, then thousands of cis women are left out. If we draw it around "privilege" thousands more are left out. If you're drawing lines that accidentally exclude cis women in order to fully exclude trans women, then clearly you're doing something wrong and your logic is flawed.
Some trans women (like myself) DID grow up as boys. Did have male socialization and male privilege. If we use the authenticity and privilege argument, then I'm not a woman. But then thousands of cis women aren't as well.
"Authentic" womanhood isn't a thing. The only single qualifier that ties all women together is that they identify as women. NOT that the world sees or treats them as women, because not all cis women have that experience either. If we draw the line ANYWHERE, we exclude some girl with some unique experience. This is a "slippery slope," of course, but it's the truth.