That can mean a lot of different things, but perhaps it hints that Cameron is playing a villainous character that is the polar opposite of her character on Disney’s Liv and Maddie.
She does play badde Mal in the Descendants franchise, but that character likely doesn’t have the same M.O.. as Ruby.
The only other clue we have is that Dove Cameron is “not an obvious fit for” the role, according to executive producer Jed Whedon.
Without more details to ponder, it’s hard to determine if Ruby will turn out to be an actual comic book character or not, but given the amount of mystery surrounding her identity, she must be important to the events of the show.