Dear Not a Racist,
The true comrade sees beyond race and gender. These are the tools that the bourgeoisie use to divide the proletariat and I would encourage you not to think of you coworker's music as "black music." Music is the language of mankind and just because your coworker's music is written by African American performers does not mean that the music is intended for a black audience.
As for your coworker, I would suggest informing her that her "private" radio is disrupting the public space of your office. I'm sure she'll understand how the greater good is more important than her private enjoyment of R&B when the matter is put in such terms.
Keep reaching for the stars!
Yuri G.