She was probably hoping that Loo Loo Land would have more people on Stolas' side than Stella's. But she forgot that most people are going to side with the person that has been cheated on instead of the cheater, even if it is gay. So then she decided that Stella would put a hit on Stolas. Which yeah, not a good thing to do, but our protagonists are killing multiple people so who gives a damn.
So then Viv was like "She never loved Stolas. It was an arranged marriage and Stolas is canonically gay." Oh, so she was forced to marry a guy that could never love her and to carry his child that she may have never even wanted in the first place. "Well, she was born evil." Oh, so she has a mental disorder that she doesn't have treatment for. "Well, she's stupid and her brother has to do everything for her." Oh, so she doesn't have the mental capacity for what is going on and is being manipulated by her brother.
And on and on it will go. The more Viv tries to show how terrible Stella, the more she unintentionally adds sympathy to this character.