If your ex-wife tried to take you to court to force you to pay college tuition, then she would not prevail.  The Supreme Court and lower courts in Pennsylvania have actually held that parents to not have an obligation to pay for their children's college expenses.  If it was part of the original marital settlement that resulted in a final decree-- then she could move to enforce that order.  However, since you were never court order and have never agreed to pay college expenses, you will not be compelled to do so.