User blog comment:Zexia0053/Understanding Extra Skills/@comment-192.223.136.5-20160124192307/@comment-27027441-20160211171530

Try hitting "switch" once at her status screen. It should toggle from Leader Skill/Brave Burst info to Extra Skill/SBB info.

You don't need to max level a 7 star to unlock their ES unless it requires a sphere item, such as the SBS units. You should only need to unlock their UBB.