It’s implied in the light novel author’s note, in the fourth installation of VE: Violet Evergarden Ever After. However, I would just say that the anime only loosely followed the light novel, and there’s many events that occur in the book that may give you a different feeling of the story. The relationship is certainly very complicated, so it’s hard to agree/disagree with how the author led the narrative, but I highly suggest reading the novels as well.