I put Tongue in on the census for SD and found that there were one or two families there in the 1920's adn 1930. Only they went by the name of Black Tongue. In some cases they spelled it Blacktongue. You might consider spelling it these ways when searching.
Depending on the age of the mother, she may or may not have been born yet, and on the 1930 census. But one of these could be her family. Do you have anything else to go on? mh