I'm really interested in how much we will stray from the very stereotypical role she plays in Turin's story (beautiful princess that sits at home, loves the main character of the story, gets captured and is in need of rescuing) - her death is really only there for Turin's character and the tragedy of the story because he's deluded into not saving her.
Personally, I don't any reasonable amount of development we can give her, with how busy these stories already are, is going to improve her character much if we don't deviate a decent amount from the text. Sure, stereotypes and tropes aren't bad per se, but in this case they sure make the character either very predictable and boring (if you expect no twist) or very dissapointing (if you expect a twist).
I think this is a pretty difficult challenge - my personal inclination would be to just cut Gwindor completely and give Finduilas his role in our series, but that's probably too extreme for the taste of most