"On top of that, nobody from Cloyan knows who she is". What even? Would it be surprising if nobody knew of this random maid in the castle? Before she came under the prince, she was well-known for being really bad at her job as a maid. That information should be easy enough to find. But they're like herp derp, she's too talented to not have been known back then?
And what is this? It's pretty well established that when the Cloyan Kingdom was conquered, it was basically a slaughter of the royal house (except Marie, obviously). Is it not at all surprising that no one knows about this random maid? The obvious explanation is that everyone who did know is dead. The level of suspicion around her is a bit too high.