Anastacia comes to mind, although she moved away from dance on her last album.
It's really hard to think of any. Most of the ones I think of are more pop artists who do occasional dance tracks. Seems most dance divas go largely uncredited or as a member of a group or as featured artists on other acts hits.
Martha Wash and Jocelyn Brown never became solo stars but they did vocals on loads of huge tracks.
Some solo divas I thought of: Robin S, Ultra Nate, Crystal Waters, Grace, Kristine W, Amber, Alice Deejay, and Dannii Minogue