What makes you think divemedic's response is lacking?
He's spot on. Your bankruptcy should not affect your spouse and anyone can sue anyone for anything.
Whether or not they prevail is another matter entirely. Yes, Amex COULD sue your wife but they wouldn't really have a legal leg to stand on, as authorized users are not responsible for payment on the cards they use. But there is nothing under the sun that could stop them from trying.
If you're this worried, you ought to look into a consult with an attorney in your area. First consultation is usually free.

