I don't know if you're "sunk," but you really don't have much of a case. Your employer has every right to extend your "trial period" for any reason she wants -- even for no reason at all. There's also no law that requires your employer to be nice to you, rather than "autocratic" and "demeaning."
Unfortunately, in your situation, if your job is not worth putting up with your supervisor's authoritarian style, then you probably should be leaving. In any event, you don't have a legal basis to sue your employer.
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