I feel like Amber is designed to be the character you're supposed to hate. As such, I've never actually had a problem with her. I like her fight, as well.
Funny you mention wishing to fight her alone, because I believe in early versions, that used to be a thing. You would have a choice between who you think is the strongest. If you chose Melia, you would fight with her. If you chose Amber, you would fight against both by yourself. My problem with this is that this decision would affect relationship points. I don't know if they'll mean anything eventually, but if it did, that wouldn