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?)
I'm as sceptical as you are Rhiannon about most of these things but you can't experience what another person feels within them. They don't have to prove anything as they are already experiencing it but it doesn't mean you are going to. We all seem to be tuned in on different wavelengths with the exception of a 'chosen' few who see or detect something nobody else does. I can't explain it in any other way, maybe there is someone else here that can.