The site reports that Natalie Dreyfuss (The Originals) has landed the role, and they had this to say about the character:
Described as possessing a fierce intelligence and a spitfire personality, Sue Dearbon is the daughter to one of Central City’s most wealthy families. But there’s much more to Sue than just the socialite reputation that always precedes her, which master detective Ralph will discover when they finally meet later during Season 6.
Expect this recurring role to first be seen later this season. You can read TVLine’s original reporting here.