Control+F may be your new best friend, if you feel unable to just politely decline and carry on using the accurate and perfectly respectful 'she' for a woman.
After writing your emails with 'she' in them, control F will allow you to search and replace 'she' with 'they', however it will leave the clunky singular 'has', 'is' intact.
Which will leave you with something like
"They has asked me to use they/them pronouns, and although I'm struggling to contort my language, they is my line manager, and I fear for any sanctions they is likely to impose on me if I don't comply well enough. They was very clear in an email that they is expecting full compliance from me."
Although policing other people's perfectly natural, respectful and grammatically correct language is unacceptable in my opinion.
Pronouns are Rohypnol, and all that.
As to the comment made by the poster who drew a false equivalence between referring to a woman as 'she' and a man espousing sexist views, I'd say this: There is no implicit disrespect or suggestion of inequality in an observer referencing another person's sex with pronouns. There is no right to compel a person to lie, and I anticipate Maya's appeal to be successful.
Even the debates in the GRA brought forth from the government that citizens would NOT be compelled to pretend a subject's sex was different, and that no sanctions would be imposed upon those who would not play along with a lie.
Judge Tayler massively overreached in his judgement.