The Butterfly, first African-American costumed superheroine, appears in HELL-RIDER #1, cover dated August 1971.
Considering that comics so often follow trends, Skywald Publications very much got ahead of the curve on this one. Pam Grier had yet to achieve her breakout status with COFFY (1973), though she had appeared in a few movies that might have been playing in theaters in 1971, though said movies were not built around her, and anyway the Butterfly doesn't seem to owe anything to Grier's persona. I frankly can't think of any other regular female character of African or African-American ethnicity that functioned in a martial capacity...
With one exception: Zulena, the wife of Natongo, the black partner in Gold Key's BROTHERS OF THE SPEAR feature, which ran as a back-up in TARZAN from the early 50s to the late 60s. The "Brothers" were the stars of the show but both of their wives were also adept with spear-play.