What was she thinking! Every bride knows to avoid fall weddings and, if necessary, to check the football schedule. Maybe she was confused and just thought of it as an away game (tolerated, but still not a date one should choose).
That being said, the wedding comes first and you will of course attend and support her 100% while acting the perfect gentleman. Afterwards, you may never let her live it down, and she will owe you her adoration as well as love forever as the perfect brother.
Note: Kudos at any and all family functions are to be expected.