White Diamond has the keeps the main melody for the trio. Instead of trying to do an impression, I'd mush rather the singer find an inflection they prefer for the right feeling with the type of voice. For White, think of a show-off kind of mother during the song. Here is a link to an isolated vocal track that I recorded in order to make it easier for you to stay on key and pitch. Have fun with it!
https://soundcloud.com/feralady/white-diamond