Board Thread:General Discussion/@comment-4698889-20171205212736/@comment-6986530-20171206022453

It is also possible, though, that while Ma knew that Postman was Waiter and that Waiter was responsible for saving Gammon, she didn't realize that Postman had regained her will and ability to speak. Postman pre-becoming Waiter was implied to be capable of communicating nonverbally and (I think?) of making minor secondary decisions.