Responses
I was using the plot from 'The Villainess Loves' as the basis for my theory. "Maybe someone or something sent Yulia to another world to learn from her mistakes" sorta thing.
Spoilers ahead (for The Villainess Loves):
Spoilers from the comments said that the og Princess Litia was the sister of mc, who basically swapped souls so mc could still live. Mc, originally from Korea (I think), was sent there by said sister (og Princess Litia) as a way to save her - or something pertaining that story line.
I'm guessing that the current empress, Yulia (?), is the same as the og empress. Considering her habits are the same (well, only one was mentioned) and how no one has realised that she's changed, especially those that have been close to her since she was young. And if this fact is already known, then... ╮( ̄▽ ̄)╭