Well, I'm not sure but aside from not knowing what she looks like, Princess Morina I mean, Marie isn't exactly the only person who survived the war and turned into a maid who now serves in the place. Also I kinda think that a Princess would never be able to clean something properly, bake/cook, prepare tea, learn musical instruments, learn CPR, sculpting and learn about the different religions of another empire.
There were a lot of maids taken in as war prisoners so they can't find her I guess.
Lol the last part haha, anyway that made sense .. thanks to both of you for answering
The story is reallllly good but I don't quite understand why they can't connect her identity to Princess Morina when they know that Maria is also a pow from Cloyan.. (or maybe I just missed a minute detail)