I think one should demand the same respect for the mythological material and characters as for the prior depictions of DC characters. When looking at how Circe has been portrayed from the Odyssey forward you find a couple of points that I think are rather constant, and should be considered part of the core character:
- The island. Circe always lives geographically secluded. Within her domains she is very powerful, but she does not leave them (unless she goes to find a new island).
- Herbs, potions, and enchantment. She is a powerful sorceress, but her powers also have limits.
- Sexually free, or at least hedonistic. Her relation to men has changed over time, but arguably a lot of the myths around her concern male fear for women who they cannot control, but instead control them (possibly by turning them into beasts, i.e. controlled by their primal urges).
To me, the parallels with Poison Ivy are rather striking. I don't view Circe as evil, more as primarily concerned with a rather narrow set of interests. She can be a useful advisor but also a rather serious obstacle.