Board Thread:General Discussion/@comment-4698889-20171205212736/@comment-2602:301:77AD:9270:79A7:EDD9:C69E:A667-20171206021604

Regardless of whether or not this makes sense to you, this is the explanation that mothy has provided. Perhaps Waiter put on a show of being a different person. Maybe the events in CF didn't happen as described (wouldn't be the first time song canon differed from book canon). The logistics of it aren't explained, but it's pretty clear that Waiter put on a pretense of being Postman after getting a new body, as it's in her Postman guise that she kills Ma.

So Ma wasn't the master chessmaster that she thought she was.