No further spoilers have been leaked about the Nicole's character but it's rumored to be surprising. Showrunner of Scandal Shonda Rhimes has confirmed the news on her Twitter account, Wednesday.
"We have Jasika Nicole (Fringe's Astrid) guest starring on ep 219 of Scandal. Which makes me go totally fan-girl with excitement."
UPDATE: Her character has a deep connection to an existing character.
Source: TV Line