I noticed that certain prayers in Spanish address María as "Madre mía".
I'm wondering whether this phrase (where it's kind of the equivalent to "oh my God") is understood to be invoking Madre de Dios, or one's own mother.
Are both possible?
According to this article, the expression refers to Virgin Mary, the Mother of God and our Mother, according to Catholic dogma.
The article says: "...aunque hay madres mías referidas a esa señora que nos ha parido, este que tanto empleamos parece tener un origen religioso que se refiere “al amparo que siempre se ha atribuido de forma especial a la Virgen”. (My translation: Although "my mother" can be used to refer to that woman who gave us birth, this expression we often use seems to have a religious origin connected with "the protection that has always been especially attributed to the Virgin.")
Mainly in the past (although some of these can also be heard nowadays), even more profoundly religious interjections were used like:
In Portuguese, there is a very usual interjection with the same origin, which is Nossa (derived from "Nossa Senhora", which means Our Lady).