Need? Absolutely not. Could we tolerate another white female rapper—perhaps one day even ascending into liking and enjoy her music? Maybe. But please don't let it be Chanel West Coast.
Capitalism loves taking black ideas, trends and styles and slapping them on a white body for profit. See: rock and roll, twerking/Miley Cyrus, Jen Selter, nail art and most recently, Iggy Azeala. The funny thing is, I don't think anyone would have much of a problem with a white female rapper as long as she was actually talented, authentic and wasn't a problematic minstrel show à la Iggy.