Marriage around the corner; Life changing decision; Things are really wierd and uncertain; ANSWERS - PLEASE!!!

I feel as though one year of background info is necessary, but not feasible - I'll try. She is from Europe and has no family here. She's living with me and my immediate family in in town for the wedding. It seems as though she can't sincerely get along with anyone in my family. One day she says she's not ready, the next day she says she loves me sooo much and none of her problems with my family matters...back and forth we go & it's driving me crazy. How can someone be certain they want to get married, but contemplate the very idea on a daily basis??? Sure, she's nervous - but she's displaying behavior that I'm uncomfortable with. Are things supposed to be this crazy 3 weeks before a wedding? Shouldn't we just be consumed in each others love and not show skepticism? I only want to get married one time to a woman who has the character to manage the difficult scenarios life inevitably throws at us. Why am I now questioning the sacridity of our marriage. Time is running out... Go for it??