It may just be that you didn’t know she already is, best way to do it it’s just flat out ask her,

Have you ever slept the black guy?”. I heard from other girls that is true with they stay about them.

Make her comfortable talking about it and being honest about it, by edging her in the right direction, be comfortable with her saying that she’d like to try it, let her know that true love it’s being supportive enough to go after your fantasies and desires.

And keep pushing how hot you think it would be if she would to go with black guys.