Jane Eyre is—drumroll please—the heroine of Jane Eyre. She's an orphan in nineteenth-century England so, like everyone in that category, she's got a hard-knock life. When she graduates from the orphanage she gets a job as a governess and ends up falling in love with her hot boss and they're all set to get married when—now's the real drumroll— he's already married.
So yes, Jane Eyre is the heroine of the book named after her. But that's not the character postcolonialists like to talk about. It's all about Bertha Mason. "'Wait—who?"' you ask. None other than Mr. Rochester's secret wife! She's been locked up in his attic this whole time. She's the one who tries to bite people and burns the whole house down.
Why do postcolonialists, especially postcolonial feminists like Gayatri Spivak, adore this loopy arsonist? Chalk it up to her Creole ancestry and the fact that she's from the Caribbean. But it's not just that Bertha's a mixed-race wild child from Jamaica—it's that Charlotte Brontë's different treatment of Jane and Bertha shows how the virtuous white Western European woman (Jane, in this case) serves to define the colonized woman (Bertha) as the crazy, monstrous "'Other."' Or—in lit speak—psycho Jamaican Bertha is a foil to saintly English Jane.