Answer:
its called "princess in waiting" and it begins in genovia, its basically about how mia and Michael first get along and mia spends a lot of time trying to figure out how to find out if Michael is really in love with her. mia also figures out what her special talent is (why she is in G and T)
the plot is here: http://en.wikipedia.org/wiki/The_Princess_Diaries,_Volume_IV:_Princess_in_Waiting