Seriously I think the next time she threatens to kill herself you need to dial 911. They will hold her for a psy evaluation and she could possibly get the help she needs. Do this out of love.
She could possibly suffer from a borderline personality disorder or bipolar disorder.
Do not agree to not bring up the affair- EVER. Heck I would go so far as to tell her that you will follow the advice of an attorney but it's unreasonable for her to think her lifestyle wouldn't change in the case of a divorce. That naturally she'll need to get a real job like everyone else- and that she doesn't deserve alimony in the first place- but that's just me and I'm not a proper DB anyway.
