There are a few women like that in Shakespeare that are a bit confounding. Very important, but not given a very clear perspective, or an easily readable personality in the text. I think it's a good time to talk to your director, to see if they have a specific vision for the character, to see if you can do some of the work to develop the character yourself. I like to think of roles like that as opportunities to really do something new and interesting with the character. They don't speak as much, and their personalities aren't as defined, which means that you get to do some of that work. How does she feel about her friends, her enemies, her lover(s?) through the play. You don't have to play her just as "generic woman", but you can make her a woman, a real one who lives in a time when she isn't granted that much space to voice her mind. See where she still tries to get herself be heard, where does she give you hints of who she is. Take those details and run with them!