The reason is simple: she's a bigot. She has been successful at pushing her transphobic agenda into UK law, and she will continue to move across the spectrum because hate only knows how to hate even when they succeed.
This is exactly the reason I'm shifting from just warning people that buying her shit is immoral so outright calling them bigots for supporting bigotry. If they don't want to be bigots they can stop giving her their goddamn money.