Candy Sothern absolutely shined during her debut in X-Men #31, when a chance encounter reunited her with "childhood sweetheart" Warren Worthington III. The two knew one another before Warren entered Professor Xavier's School for Gifted Youngsters as Angel, and then would become romantically involved as young adults.
Though originally introduced in dialogue with the last name Sothern (without the letter u), further appearances clarified that her last name was Southern (with a u) by the time Angel joined the Defenders.
As far back as Defenders #121, Beast and Valkyrie were at odds about who should lead the team, while Gargoyle dodged the debate. That push-pull dynamic helped explain the group's eventual decision to appoint Candy Southern as leader of the New Defenders (#138).
For all her intelligence and poise, Candy had no real qualifications to lead a super-team—except what she might have learned through osmosis over the years as Angel's girlfriend. So she was understandably surprised that the heroes selected her for the position.
While in charge, Candy focused her attention on improving the security system of the group's headquarters (#145), acting more like an honorary leader than the real thing. But a non-leader was all the New Defenders could agree on at the time.