I work in a long-term facility and I've come across several women with this name. I'm in North Dakota. It's normally spelled this way. All the women are 70-90.
It's a submitted name, but there is little information on it. I also did a search on this board, the only information that came up was that it might be Filipino. Considering that ND - at that time - was almost exclusively Scandinavian and German, it seems unlikely. I know, however, that Juanita was also popular at the time and I've bumped into two Bonitas, I suppose it's not out of the question.