I am not a lawyer but unless she was under some sort of duress when she signed I do not see how this cannot be overturned.
Can it not be argued that springing the pre-nup on her two days before the wedding was "unconscionable" ?
I am not a lawyer either but giving it to here TWO DAYS before the wedding has been ruled to be under duress.
I think being presented with a prenup two days before the wedding - after invitations have been sent, you've told family and friends how you're so much in love, etc. - could be a situation causing duress. It would freak me out, that's for sure.
Yours is a logical attitude except for one important fact...
this is all taking place in Massachusetts!