Would you mary me?

"Do you, ___(bride)___, offer yourself wholly and joyfully, and do you choose ___(groom)___ as the person with whom you will share your life, in laughter and in tears, in conflict and tranquility, loving what you know of her, and trusting what you do not know yet?"
NO.This was the answer one of my aquintaces heard few days ago from his "potential wife" in front of the officer of civil rights. He was getting ready for the wedding, had a long term relationship with this girl. The wedding was scheduled for 2 days after civil ceremony, the invitations were sent, everything&everybody was ready and ....BOOM! She said: NO. Ouch! I feel sorry for him and I am still wandering why would a girl say NO in the last moment.Any suggestions from girls, wives, girl friends and any other experts?