The conclusion is,
She is having tea by herself, talking by herself that why the mother of the prince say that she crazy, it mean that The Real Lucia is Inside The body Of reincarnator. 2 soul in 1 body it mean
You know the real tragedy of all this, is that Lucia herself seems like a genuinely sweet friend in the flashback. If it weren't for her obsession with the harem ending, I wonder if she would've become a lovely young lady.
This unknown friend of hers is so crazy about her that it makes me think she might be some kind of secret character the devs had planned for with the data being in game but didn't implement due lack of time or scrapped the idea. Can't wait for the condemnation event. Thanks for the chapter.
In this kind of game it's common for the "narrator" to be MC's friend (we can't forget tomodaaa). Either this game doesn't have it, or reincarnated MC just forget entirely.