Of course she is an XY intersex. There are many reasons and many degrees to which the developmental trajectory can be shifted from the normal (for XY) male mode to female, including SRY deletion (which would lead to full female development including the primary sexual organs), or defective androgen production, defective androgen sensing, or defective androgen responses (which tends to lead to various intersex phenotypes). Not all tissues need respond in the same way, either.
My point is that in the case of CS the musculature still responded, at least in part, to the elevated testosterone levels that are associated with her primary male genetic makeup, especially during and since puberty.
This is the main thing that distinguishes physical development in young men from young women: Look in any kindergarten or primary school and you will often see girls that are stronger or faster than their boy classmates. Do the same after puberty, and it will be rare.
The improvement in 800m times CS experienced around age 17 (according to wikipedia) are precisely the effect of a male type puberty, suggesting that she also now still has the continued anabolic effect of testis produced testosterone.
Thus, if you bother at all with having a women’s category in athletics, you better make sure that the competitors all had female type muscle development during and from these years. Anything else, such as external sex organs, Barr bodies, or the actual genetic makeup is irrelevant.
I don’t know what the best way is to deal with the problem participation of intersex athletes poses for female competitors with normal physiology. Demanding that CS takes drugs to lower her testosterone levels, or even asking for surgery seems to me to be a massive human rights issue.
I would therefore prefer to cleanly ban XY, high testosterone intersex athletes from female competitions. Bad luck (and arguably a lesser human rights issue), but simply an unfortunate consequence of the hand they were dealt by genetics.
To me this seems the less bad option by virtue of being unfair to fewer people (compared e.g. to classic sex examinations or self classification), but of course such an utilitaristic approach to ethics has its own problems.
