the carstairs are the superior family

We got no scenes from her perspective until the wedding scene, which was poorly set up and we were not privy to any of Edwina's thoughts except that she wanted to marry Anthony. Yes, we got a really nice scene with the King and Queen, but that was the extent of her POV. Why doesn't she want to marry Anthony outside of his connection with Kate? Why is she still mad at Kate? Is she comfortable with Kate weeding out suitors or is she more like Daphne and wishes to figure them out on her own? How much do we really know about Edwina Sharma outside of what is TOLD to us?

I don't know how to tell you this, but if your main takeaway from the book is that Edwina's character is little more than a prop and "kind" then you thoroughly misunderstood the character and the book itself.

Book!Edwina is kind, yes, but she's also intelligent and perceptive and has an idea of what she wants. She wants to marry a scholar, someone she can discuss ideas and books with without feeling like a trophy. But she's also willing to put that aside to support her family, something she shares with Kate. And yes, Book!Edwina doesn't have much of a role to play in the book outside of being the younger sister and supporting Kate in all endeavors, but neither does Eloise or Daphne outside of their own books.

There are so many ways you could've expanded upon Edwina's character without shoving her greatest strengths in the garbage. You could've made her more mischievous, or actually shown her dealing with the heavy expectations placed upon her. Instead we got one scene in 2x03 to set up her breakdown in 2x06 with nothing in-between. She's innocent but not naive, kind but not a doormat, and believes the best in people. She represents a lot of women who feel like they can't say no to things because they're kind and sweet and they don't want to hurt anyone's feelings and CVD took that away from them in favor of a storyline that nobody wanted or asked for in any capacity.

To call your version of the character "fully realized" and "not a prop" is insulting to Julia Quinn's work and her characterization and I for one, am tired of men constantly claiming that their version of things is the superior one.