I’m glad that you like her. ^^ 
When I did some googling about the Unown, it said they also appear in Kanto in the Tanoby chambers on the Sevii islands. And that they appeared in the Adventures manga there. But I think it would be really cool to find another ruins in the mountains somewhere that contains them, as you suggest.

I’m thinking that Amy is from Kanto. But I’ll update my CS later with an official answer.