Yes Vi-vi has yet to know that he is a Mewtwo so for now she things he's a cat which... in a way he kinda does look like one.
Anyway~ In my head I imagine she just spotted him injuring another poor resident and not so impressed with the misuse of strength resulted in this.
Yes she hates it when people use their power to hurt people
Though I realize she's not going to fair well against two of his attacks so who knows what happens next~
Also... Mewtwo... your tall as ever, especially standing next to her