Those jeans, with a dressy top, will be just fine for Smart Casual nights on Princess.
One misconception that people have is that if a cruise line is owned by a large corporation the dress codes are the same. They aren't. Carnival Corporation owns: Carnival, Princess, Holland America, Costa, Cunard, Windstar and a couple more I've probably forgotten. The dress code on Carnival Cruises and Cunard are very different. Each cruise line has its own rules.
Dress jeans and blue jeans are two different types of clothing. Just because two things are made out of denim doesn't mean they are the same type of clothing.