Yeah tbf I'll give you that one, it does make it seem daft that she wouldn't mention it.
Retcon means when something that was previously established as canon (something that is accepted as being true from the author's previous works) is essentially ripped up and changed. Basically where they contradict something in the story and it becomes the new "truth". An example, in Harry Potter professor McGonagal's age was stated somewhere I think, and then in the second fantastic beasts film she is seen teaching at hogwarts, when actually she should be a student or a young child. So there they've changed the story and we have to accept that the previous source material is wrong