Can a wife be liable for the pre-marital medical debts of a husband?

A debt is a debt, being for medical expenses doesn't change that. So the wife should seek legal advice on how to keep her money and financial affairs protected afterward in the state in which they live (pre-nuptial agreements were invented for this stuff). She should also want to talk with the attorney about estate planning and living trusts.

This is a tough one. I want to say no because the medical bills were in his name being applied to his credit report. However, the other thing you do as a married couple is share all assets and liabilities brought to the marriage and occurring after the marriage. Maybe a wife can cover expenses if she carries him on her health insurance, but most insurance companies would consider bills acquired before marriage to be pre-existing conditions.

Forget common law.

Many states have statutory law where the spouse becomes personally liable for all debts of the other spouse upon marriage.

for better or worse, for richer or poorer, til death do you part.