Arlene Campbell was the wife of Christian Campbell.
Arlene and Christian were trying to have a baby, a fact noted by Samuel who asked Christian how they were doing on that front. Christian admitted they were having no luck. This inspired Samuel to have Arlene and Christian to adopt Bobby John, much to Dean's chagrin, who did not want them raising a shapeshifter.
Christian never got to claim the child, however, when the Alpha Shapeshifter came to collect Bobby John.
It is unknown what became of Arlene after Christian died. It is hinted at that she was spared from Azazel's purge of Mary's relatives, making her one of the few remaining survivors of the Campbell Family.