In the first season, Mariah is a suave politician. She mostly makes calculated moves, unlike her cousin, Cornell, who's impulsive. As an additional contrast with Cornell, the former is willing to refer to himself by a certain racial epithet, while Mariah seems to find it offensive.
She definitely does have the potential to lose control of herself, as we see with one particular incident. But overall, she seems composed.
However, by the second season, her character seems to have changed a bit.
She seems to be a lot more emotional. She's faster both to celebrate, despair, get angry....
She also seems to be pretty open with public displays of affection with Shades, which doesn't seem much like the way she was acting last season.
She seems to have adopted Cornell's willingness to refer to himself by said racial epithet.
She still retains her former distaste for the family business, despite having taken over; indeed, she's trying to get out.
Now, part of this could just be my perception, and the first season was some time ago, but she seems to have notably changed.
Why is this? Is this part of her character evolution? Was it a directorial choice? Is the intent to show her acting more like Cornell?