For many years she identified as a crossdresser and it was (at least in part) a sexually charged activity. Now with the administering of female hormones she is noticing that the sexual energy is dissipating.
This is not at all surprising.
What happens to most of us is that the activity becomes taboo early on and takes on an erratic nature which includes periods of purging. This adds to the expectation of getting your next "fix" which only even more builds anticipation and sexual energy.
As Sophie has gone on to a new norm she is noticing that women's clothing has taken on a more pragmatic function and just "feels right" rather than being a turn on.
What this suggests, as I have said here many times, is that treating the dysphoria through cross gender expression and or transition gets you off that roller coaster pattern and mormalizes things.
You will also note that even if the HRT dampens the male sexual drive the identification with the female identity remains completely unperturbed.
Watch her explain....