wanting to protect your wealth is natural, if things go wrong its normal to want a fair agreement,
if shes happy to sign a pre agreement then thats good, im sure if things went wrong you wouldnt see her with nothing,
from experience, the person you love and think you have known from years of marrage, can turn out to be someone quite different in a divorce situation,
but hopefully you will never have to face that,
but i will say real love is worth more than worrying about money