Does anyone else get chills when they think back to “Home” and Mary apologizing to Sam and Sam asking, “For what?”
But the angels, in fact, DID erase her memory! Two times to be exact. First they did when Castiel sent Dean to the past with the mission to prevent the whole thing (Dean told her to be extra careful on said day) but she was not allowed to remember is warning.
The second time it was Michael, after he took young John as a vessel after Anna’s try to kill mary before she could give birth to her sons.
So maybe she couldn’t even remember ANYTHING? Maybe Michael changed ALL of her memories and made her forget about the deal, too?