I see I'm in the minority here 😅. I think she is. I feel like this is the way to "announce" it with these two. It's not going to be flashy. Also, I'm convinced that Violet is mouthing "pregnant" as she's reading the letter. Additionally, you do have some gaps in time between the first time and this scene which would make it plausible for her to know by now. Lastly, I feel like this scene is her fighting for herself, as well as them as a future family.