Either this is a joke, or you have not looked at any recorded history of judicial proceedings. Judges often have incredible power with few oversights.

You do see it the most in situations like this, where the accused is a target of the state or poor or otherwise can't defend themselves.

Why is the judge guilty of perjury? Certainly her decisions have been questionable, and she will probably be criticised by the High Court, but perjury is specifically about lying under oath -- and she hasn't done that.

Clearly, she has not lied under oath. It is the prosecution that lied in misleading the witness on material facts, in which she is assisting. In these new times we might say she has conspired to commit perjury in High Court.

Prosecution can't commit perjury - only witnesses and interpreters can, given the statutory basis for perjury which is preferred to any common law perjury.

She might've committed misconduct in public office.

Yes, they are - but it's not perjury which relates specifically to witnesses and interpreters. It could well be misconduct in public office, or something though.