Reimu is fundamentally a person who notices incidents and then deals with them.

With that in mind, we three are the only ones who know so far, but Reimu just doesn't know yet.

...I'm happy to have your approval, Keine, but won't there be any issues with the Village?

I can't say for certain, but she should be "innocent until proven guilty". People wouldn't necessarily ostracize her even if they knew. Although...

She herself is extremely curious too

so we should probably keep an eye on her.