Not sure it's actually "sexist" Galaxy, perhaps as I tried (and failed) to explain, it's someone revelling in the newly found feminine aspects of their life?
Yes, David/Diana does write about enjoying "swishing" their expensively acquired hair, and trying to adjust their voice to a more female timbre, but as it's written by someone transitioning from make to female, and hoping for (and planning) the ultimate change, i.e. surgery, which is not undertaken lightly and involves psychiatric consultation as well as consultation with the surgeon who might be carrying out the procedure, I'm not sure that I can support your view of the column being sexist.
David/Diana has lived as a man, is in the process of becoming as much of a woman as he/she can.