Not so much an evil villainess as she is a shrewd and cunning manipulator. It's all dependent on the motivations. In the OG timeline she had nothing but revenge pushing her no matter the cost which would bring everyone ruin, she was on her own with no one but herself, so naturally she'd be selfish and wish everyone else's ruin. In this timeline it is the same, but she's doing it all for Emi's sake. Emi had such an impact on her for loving her for who she was, that it gave a heartless Remilia something to strive for. She was also just content being a bystander in her own head, watching Emi was enough… until bitchtits came along and ruined it.
"Emi established me as a young lady with the notable reputation of the Duke's daughter. I, Remilia Rose Graupner, will not commit as grave a mistake as falling for this."
A nature vs nurture argument. It's in Remilia's nature to be a fantastic schemer with a sadistic streak, but given a just cause and a healthy upbringing (through Emi's memories) she can turn that talent for good.