Think About This : Her life was peaceful and beautiful her "father" was the Emperor and her "sister" is super nice to her. It's like her life is from a fairytale! She lives in incognito with this fluffy prince-like boy. Who knows, what if he was her prince charming who sweeps her off her feet? After all, her life is like a fairytale. He will always be there for her like everybody else.
Janette is truly kind and special. However, almost everybody is super kind to her, and she expects that out of them. Like they have to like her and if they don't like her right now, they will later. After all, she feels like the princess of a fairytale. Or at least I think she pictured herself as a magical fairy princess. It's because of Mr. White who keeps on telling her what she expects that she believes it so much. And then there's her self esteem, She "says"(her thoughts) that she feels bad for thinking that SHE (Janette) would get married to Izykiel (or something) she feels bad for assuming that SHE would be the protagonist of this story and instead thinks that it should be Athy.
The fact that she thought of this scenario shows how she condisders this as a something that should happen, because she just assumed that way. I'm guessing her mother was like Janette when she was younger, but then grew jealous or something. I have a feeling that Janette will betray Athy in some small form or way because how much she wants a Family or longs for love. However, considering her current meek personality, if she was given memories of the previous life, she would give Claude up to Athy and run away or something due to guilt.
100% sure that I'm not 100% correct. There's a chance that she actually does have the FL syndrome (she has them symptoms~) but I just can't explain it too well.