I think the WBW is about to test Ahsoka and so that’s why Anakin is there but there’s a few things wrong. He has the wrong hilt (a clue for Ahsoka) and Vaders theme played (a hint for viewers)

I think she’s going to have to come to terms with the fact that this was Anakins destiny all along and even her staying in the order wouldn’t have saved him.

When she accepts that and accepts that she is not responsible for what he became and what happened she’ll be able to leave the WBW and it’ll likely make her a less apprehensive master to Sabine.