1. Who's The Bride?
When you go to a wedding, there are unspoken rules everyone has to follow. Don't get too drunk, don't get in a fight, and whatever you do, don't show up in a white dress. Traditionally, the bride is the only one who should be wearing white because it is her big day, and she is the center of attention.
Unless the invitation stated for people to wear white, or the bride approved your white gown, it is so rude to show up looking like the bride. The bride seems angry with the guest, who decided to steal the spotlight. It was an uncomfortable situation to witness.