NEOMA told Hanna about her first and second life after her cousin covered the entire tea room with her Shadow Veil. Since they couldn't call a servant, Lewis volunteered to clean the pieces of the broken teacup on the floor.
After that, she proceeded to tell Hanna her other royal secret.
But she omitted some fact.
Regarding her first life, she told her cousin everything she remembered about it. But she didn't have the heart to tell Hanna that Nero killed her because she got involved with Dahlia– the Black Witch that Nero of her first life was obsessed with. She just told Hanna that Nero killed her back then because she tried to perform a forbidden spell that would tie her life with his.
About her second life, she didn't tell Hanna that her dad/appa in that life looked like the former Commander Gavin Quinzel. It just didn't feel right to tell her cousin about her family matters when she hadn't begun her investigation yet.