Dear Princess Diary,
How was this SUCH A SECRET? Was it that she didn't know Genovia existed, or she didn't realize that she's half Genovian or did no one genuinely care about the Genovian monarchy? Also, why is the monarchy still in rule? AND if a monarchy IS still in rule, how is it that nobody (i.e. the news/her mom) keeps tabs on her - allegedly, their NEXT RULER.
She's there for, like, a few weeks and not only does she have this HUGE mansion, but it has all of her belongings, a garden, memories? And why did Mia never know about this mansion? Or if she did, how did she forget about the security and the intercom and the "no walking on the grass" thing?
Why does a territory that has been established so long ago that it is currently ruled by a monarchy not have an accent? Or a language? Everyone speaks in various accents; their QUEEN has a British accent, while her son has a mid-Atlantic/American accent from the 1940s.
Just because you want your kid to grow up normally, like other kids who live in a firehouse and whose moms are dating their teachers, doesn't mean you have to hide WHERE SHE COMES FROM FROM HER. By that token, terrible grandma! She's literally never seen her granddaughter until she remembers her mortality and her son's death and realizes that she has to secure her family's position as leaders of Genovia. And then she assumes (apparently, rightfully so) that she can take control of Mia's life. And change the way Mia looks because every world leader needs a makeover. ;)