Serena Williams will meet Jelena Jankovic in Sunday's final after the ninth-seeded Serb overcame Switzerland's Stefanie Voegele 6-4, 6-7 (6-8), 6-2 in the day's second semifinal.
Defending champion Serena Williams breezed past Venus 6-1, 6-2 in the semifinal match -- their first meeting since the finals of the 2009 WTA Championships in Qatar, and the most lopsided of 24 career encounters between them.
Serena's fifth straight win over her sister gives her a 14-10 lifetime record against Venus, the 2004 Charleston champ.
The elder Williams looked fatigued in the match, committing eight double faults while converting just 52 percent of her first serves.
The triumph gave top-ranked Serena world a 10-match winning streak heading into the Charleston final.