I haven't modded or played GTA V since last summer so I'm not too sure about ped mods. Unfortunately black girls are difficult to find (for any game really). Although, GTA V's female pedestrians aren't that bad, actually some of those black girls are gems.
Anyway there's not much for GTA modding here, you're best bet is too look at more dedicated modding sites for GTA.
Baby it's your world, ain't it?
Nicki is my Mom but Tay is my Queen