If you're interested in getting some evidence for her skill it would be so so easy, you could blindfold her before you get there and then lead her randomly round the stones (or much better still, get someone else to, who doesn't know which is the particular stone). You'd not think a blindfold would prevent detection of whatever emanations they're supposed to be?
Would that not be brilliant? (and I'm not denying I'm sceptical about these sorts of things. But what's wrong with a bit of evidence? I would really like fairies and thylacines to exist. But a worldful of hoping doesn't make them real unfortunately. It's easy to convince yourself about things, the mind's a powerful thing. But surely there's nothing wrong with a bit of hard evidence to convince other people?)