The application probably asks for “gender,” rather than sex. Most forms do these days.
Anyway, if they bought her being a man during the interview, maybe they could have just let her work, see how she did with clients.
Then they need to change it back, and never tell anyone the real reason for being fired. I never fired anyone for any reason other than eliminating their position due to cutbacks. As nice as it would be to help people grow for their next job, predatory lawyers are too big a danger.