JAZZ WOMEN'S HERITAGE SERIES: Big Mamas: ''Independent Women's Blues,'' Vol. 2. Rosetta Records RR 1306. This sequel to ''Mean Mothers,'' brings us another priceless collection of early female blues singers. Produced by Rosetta Reitz, who has spent many years ferreting out rare recordings of famous and obscure blues ''mamas,'' this set includes 16 singers on recordings that span the years 1925-1953. Among them are Ethel Waters, Ida Cox, Billie Holiday, and, surprisingly, Hattie McDaniel, who was best known for her role as Mammy in ''Gone With the Wind.'' Not too many know that she was not only a singer, but a drummer, and was nicknamed ''Hi-Hat Hattie.'' Rosetta points out in her liner notes that in the l920s, more than 75 percent of blues recordings were made by women. And these women were often accompanied by top jazz musicians of the day. The point of this series, aside from the obvious one of reissuing these fine old recordings, is to show a positive side of the blues, where women aren't bemoaning their fate, but rather asserting themselves in a way which is spunky, vigorous, and often very humorous. It's a bit racy for some listeners, perhaps, but nonetheless important historically for collectors of this kind of music. Most of these cuts are reissued here for the first time, and the quality of the sound and the pressings is excellent.