The 55-year-old actress stars in the titular role of the drama movie as a fiery black musician who is engaged in a battle of wills over control of her music in 1920s Chicago but she believes it is down to the audience to judge if she is a protagonist or antagonist.
Viola said: "I don't view her as a protagonist or antagonist, because I can't. An actor doesn't do that."
"It's like, you've got to portray the character exactly who they are. Whether they're a protagonist or an antagonist, that's for the audience, that's a judgement."
The Oscar-winning star explained how she played the character in the Netflix movie as a woman who wasn't valued in the film's setting but as understanding her worth as a musician known as the Mother of the Blues.
Viola told CinemaBlend.com: "I portrayed her as a woman who literally is born in the world that doesn't value her at all – that doesn't even recognise her as a human being, but she is a person who understands her worth."
"So, therefore, she's a woman who absolutely has busted a hole through 1927. She is a liberated woman."
The "Widows" star continued: "So I just saw her as a woman who knew her worth and wasn't going to concede. It wasn't up for discussion."
"I know that (as Ma) I'm great at what I do, I know it's making you money, I should be called the Mother of the Blues. I'm influencing all these other singers, so you treat me like I deserve to be treated. And that's it. That's how I saw her."