Interestingly, the word consuegra means something for which there is no word in English.
suegra is the mother-in-law. For any given couple, there are two mothers-in-law (and two fathers-in-law), right? To each of them the other mother-in-law is the consuegra.
To make it clearer: suppose you are the father or mother of Kenny, who married Rose. You are one of Rose's in-law. And Rose's mother is your consuegra!
There is also the masculine equivalent, consuegro.