In his book A Guide to the Stone Circles of Britain, Ireland and Brittany (ISBN: 0-300-06331-8) Aubrey Burl writes (citing Briggs as his source),
It may be no more than coincidence that the church [Ysbytty Cynfyn] is only 1 and a half miles north Devil’s Bridge over the River Mynach where the Devil was tricked by an old woman who saved her soul by sending her little dog to cross the bridge before her.
I’m inclined to think that it is no more than coincidence, as the connection between Bronze Age Ysbytty Cynfyn and Devil’s Bridge (Pontarfynach) is a bit tenuous. Cope makes a similar connection between the two places, but it’s not clear why.