I love Minthara too! I think it is in large part due to her fantastic voice acting! I was repeating the "oh dear, Sazza" line in my head for days after hearing it! I also just loved her conversation with the Goblin Warboss, the "I'll take something precious from you every hour that passes" also the way it describes a "cold hand caressing your thoughts" c'mon. They were trying to get people to love her, and it worked!
Yes, her cruelty has its own charm and sexuality. The voice acting is great, but some don't like it