It was collected from a mrs ben daugherty , in 1958,in kentucky.The song dates from the american civil war,so is not very old.
your quite right it is often referred to as the creole girl, but most versions have,the lyric at the end of the first line, The lake of ponchartrain.
Now the lake has been in existence for over 2000years ,much longer than the song, and the residents of loiusana and america know the lake, as lake ponchartrain.
If I was to sing GEORDIE and sing as I walked over london bridges,it would be equally nonsensical, LONDON BRIDGE is a specific bridge it is not Tower bridge or Blackfriars bridge.The lake of pontchartrain is a specific lake.THE PEOPLE OF LOUISANA use this title ,to my mind this makes it correct