Complex sentence: In SCEF, Baker worked closely with her friend, longtime white anti-racist activist Anne Braden, who had been accused of being a communist during the 1950s by the House Un-American Activities Committee (HUAC).
Split into simpler sentences: In SCEF, Baker worked closely with her friend Anne Braden, a white, longtime anti-racist activist. Braden had been accused in the 1950s of being a communist by the House Un-American Activities Committee (HUAC).