Well, even if it's known she's the saint, there is now a knight order who will jump in front of an arrow for her.
If this was a darker story, the higher ups would start to get worried that Sei could end up unintentionally launching a coup.
If you think about it, the so-called once in a lifetime prophetic dreams that got her free art supplies was worth about 120 dollars.
I'm not sure that's worth being so impressed...