When the original actress that played Naevia (Lesley Ann Brandt) decided to leave Spartacus, I was initially disappointed. But it ended up turning out for the best. Not only was Cynthia a more capable actress to handle the new material, but her chemistry with Manu Bennett was far stronger; it was organic dynamic between two people. Whereas before, the only thing Crixus and Naevia really did was make out and/or have sex (and perhaps exchange a few words here and there, but never a full conversation). And while raunchy love scenes and declarations of love behind bars with the first actress is what more simple minded people will immediately conclude as better chemistry, that was not needed with the new actress. They only needed to look at one another to convey the same feeling of emotion (it is quite remarkable that she and Bennett never had any real love scenes in this show). For me, the character Naevia did not feel like a real person until Cynthia stepped into the role. Forever grateful that the original actress was replaced.
As seen in her other minor roles (Colombiana, CSI, Numb3rs, Dallas, etc). she can play a wide variety of characters. Cynthia now plays Amanda Waller on "Arrow". She currently plays the best live action adaption of this character. Easily could have played as angry and over the top, but instead, calm and collected, with a soothing voice.
Cynthia continues to grow more as an actress with her newest turn in "Texas Rising". As Emily West she speaks with much style and flare, and over the series have shown every side of a multifaceted character; sadness, vengeful, seductive, rage, caring, vulnerable. Probably her best role yet.