My mom is going through rapid memory loss. She is to appear in court and give a statement. I'm her POA, can I give the statement for her?

Yes, need more info about what kind of statement. If not having to do with her cognitive ability, then I would get something from the doctor saying she has Dementia.

Quite - it must partly depend on what the hearing is about. But thinking about it, whatever her statement it has to be her statement. You can be there to support her, but you can't do it for her.

If the hearing does relate to her care or wellbeing and it's in a family court, I would expect it to have well-established procedures for treating vulnerable people sensitively. Why not ring them up and ask?

What sort of hearing is this? Do, some not believe she has dementia? In t that case,  part of the reason for the statement is for the judge to determine competency. Check with your attorney to see if there is an option for mom to meet one on one with the judge. No courtroom intimidation.