i have read all the interview questions, and i am sure she will be ready to answer anything they ask, but just i was wondering....the ones that have gotten the blue or white slips, what was the reason for this?....is there a list of reasons as to why they often give these unwanted color slips?

there are various reason that different people have to get a blue or white slip
if i were you just come prepare and bring along enough evident to provide your relationship

more is better than not enough

some people get turn down because of materials that they bring with to the interview
another thing understand your relationship inside out will help <<<<<< if you don't they think it a praud case
and might give you a white or blue slip

Setting aside blue slips for missing information, most blue slips stem from concerns about the bona fides. Knowing each other very well and being able to show it is the best medicine.