So I'm writing a fantasy novel, and I have my plot fairly fleshed out, and I have my main players, my world is built, and now I've started to really flesh out my characters more. The only problem is, I've already fleshed out about 5 of my secondary characters, and it's really starting to feel like my main character pales in comparison. I'm not quite sure what to do.
For the purpose of the book and the plot, the main character the way I've imagined her, is a shy and unsure girl who is actually quite determined. She's thrown into a new world she doesn't really know much about (as YA protagonists frequently are, y'know...), where she kind of feels inadequate and out of place (obviously). I want her arc to be that of overcoming her own self-doubt and fear, and doing the things she needs to do in spite of her fear. Only, I feel like every time I put her next to my other characters, she comes across as annoyingly shy and mousy. She's more of a secondary character than my secondary characters, and at this point the way I feel about her is, if I read a book with a character like this, I would hate the hell out of it. I think this is because she's not fleshed out enough but I just don't know how to build her up while keeping her personality consistent.
I feel quite stuck and I was wondering what tools/ideas/techniques/things could help me see her in a different light?