Originally Posted by Luke_Y
Would not compañera, pareja, or even novia be a kinder description?
I think they used "concubina" as part of the journalistic jargon used in police reports. The colloquial term would be "pareja".
In any case, "concubina" is not demeaning in Spanish, it only describes the legal
form of engagement: it means they live together. In many countries of South America
that's now is a legal
form of marriage, giving rights to the partners that make them in many ways equal to the ones of marriage.