She has to be related to Mika. After all, how many people have that unspellable last name?
As I've said before, PJ, the real question should be: Is Nadin related to the more famous Brzezinski, i.e., Zbigniew Brzezinski, who was President Carter's National Security Advisor? The TV personality Mika (whom I have never seen) is the daughter of Zbigniew.
"Brzezinski" is not that uncommon of a Polish last name. If Nadin is related to ZB, it may not be close. According to public records, Nadin is the daughter of a Szymon and Joan Brzezinski.