One of the big questions of "Havisham" is this: just how crazy is this lady? Is she reacting proportionally to what has happened to her? Or was she always destined to crack? Has she brought all of her troubles upon herself or is she the victim of her cunning and malicious ex-fiancé? Is she a victim of her society, which has restricted the roles of women? Or is she just plain bonkers? By letting Miss Havisham speak for herself, Duffy raises all of these questions but doesn't quite answer them. Yes, Miss H seems a bit off her rocker, but who doesn't go a bit crazy after being unceremoniously dumped? In many ways, this poem asks us to understand, and even identify with Miss Havisham, and that makes us question our very own definitions of madness.
Miss Havisham has clearly gone round the bend. It's just not normal to live your whole life in a stinking wedding dress.
Miss Havisham is not crazy; she is very aware of the person she's become. Even though she has regrets and is incredibly bitter, she's still in control of her life.