The Princess Diaries 2: Royal Engagement (2004) on Netflix

Princess Mia has just turned 21 and is supposed to succeed her grandmother as the Queen of Genovia. But Viscount Mabrey who wishes that his nephew who is also in line to the throne to be the new ruler, reminds everyone of a law that states that an unmarried woman can't be made queen, and with the backing of parliament, he opposes Mia's coronation. But Queen Clarice asks that Mia be allowed time to find a husband, and she is given 30 days. But Mabrey tries to do what he can to stop that. But his nephew, Nicholas has met Mia and they are both attracted to each other but Mia upon learning who he is, dislikes and doesn't trust him but Clarice has invited him to stay with them for the 30 day period to keep an eye on him.