Both Betty AND Barney reported similar and corroborating stories.

Which leaves only two possible alternatives: Either it is an elaborate hoax, or they actually were abducted by aliens.

There is potentially a third variation, although I suspect it's a remote one. One of them might have recovered or manufactured memories under hypnosis (either true or false), and the other, after hearing them, manufactured congruent memories which then surfaced due to suggestion in their own hypnosis.

The similarity of multiple alien abduction reports since the Miller's encounter also leaves only two possible alternatives: Either subsequent abductees have used their story as a model for their own, or the aliens still haven't learned everything they need to know.