So it feeds with Chaffinches, looks like a Chaffinch with some aberrant white feathering and - if that photo is of
the bird (and I suspect it may well be as it sure as anything isn't a "stock" Snow Bunting pic!) it IS a Chaffinch!
Oh - and there's not been a whisper on any of the rare bird forums/lines etc. about a garden-feeding Snow Bunting in Cornwall.
Poor lady is clearly NOT "an ornithologist", those bins look heavy, antique and possibly ex-naval (and possibly virtually unusable) and she went on an expensive
organised trip to Norway where the leaders failed to point out any Snow Buntings? Oh dear!

That reminds me of a chat I had a few years ago with an elderly lady who had been on a Norwegian coastal cruise and the "resident ornithologist" showed the "clients" a flock of Snow Buntings which most definitely were
not! I can't recall what she said they actually were, but she knew he was misleading folk because that's what they all wanted to see!
Cornwall Lady would have done better to spend a much cheaper winter weekend on the North Norfolk Coast with one of the reliable bird guides....