I think the whole premise of coercion is bullshit. If she had a lawyer present or not, and didn't like the terms of the prenup, it's her responsibility to raise her objections and refuse to sign. You don't sign, go through with the wedding, then when you want out say you were forced to sign. You weren't forced - you, as an adult, have to make a choice, even if the choice is an unpleasant one.
"The best kind of pride is that which compels a man to do his best when no one is watching."