If her mother was REW then she must carry this gene and will have around 50% REW kits if bred to the REW buck and the other 50% steel and broken steel
If the black buck has any chinchilla, sable, himilayan or REW in his history you may get one of these colours
There is a good chance she carries self so you could get 50% blacks/broken blacks if bred to your black buck and the other 50% steel and broken steel
She might carry dilute/blue and if either buck carries this gene you could get some blue based colours like broken and solid versions of blue gold tipped steel, Opal, blue