Reddit mentions of Dove and Sword: A Novel of Joan of Arc (Point Signature)

Agreed on your Bella Swan point -- she's terrible. Sabriel by Garth Nix has a slightly more admirable female (though sadly, character development isn't his focus / forte, so not much to dive into there), as do the sequels). Anna of Byzantium, while perhaps a bit young, is an awesome historical female figure, as are the various heroines of Caroline Meyer, or perhaps The Queen's Own Fool by Yolen & Harris - or Dove and Sword, a novel about Joan of Arc (caveat, these may have 1-2 racy scenes -- nothing as "bad" as Twilight, but as you are a teacher, wanted to flag), or The Many Lives and Secret Sorrows of Josephine B. -- wow I just went a tear of historical, fictionalized heroines...

John Green - I encourage Papertowns as that seemed the least form factor, but I certainly hear what you're saying. For more "unexpected" I'd refer to the Crutcher books or to Special Topics in Calamity Physics by Pessl or An Uncommon Education by Percer - the latter two having that prep school / sheltered feel to them but being unique / interesting in their own right.

Continue the good fight against Bella...