If a non royal marries a prince wouldnt that make then a queen not a princess?

The only Queens we have are Snow White, Ariel, and Belle. Snow White's parents and step-mother are dead so she's the Queen of her kingdom, Eric's parents are dead and he had to to get a wife before he became king so Ariel is queen of his kingdom, and since Adam/Beast's parents are gone that does make him the king and Belle a queen instead of a princess. The others are just princesses.

I think you answered your own question. I think only in the eyes of Disney is she a Princess, but although the Beast had no elders they still didn't have a ceremony crowning him king, nor did they ever mention his family or a crowning at all.

Aurora Merida and Rapunzel are all ready princess.

Cinderella and Tiana are the examples of non-royal marrying prince.

Snow White and Ariel, however share that with Belle. Snow's Prince maybe didn't have living relatives and neither did Prince Eric.

Pocahontas and Mulan don't count in this.

well still prince marries girl, girl become princess, even if there were no elders he is still not king so, maybe after the movie ended he became king making her queen but yah, not really a queen plus princess, queen to disney "whats the difference"

I think you have this backwards. A non royal marrying a prince makes her a princess, BUT that doesn't mean she'll be queen when the prince's elders die and make him king. That goes for common boys marrying princesses, too. Queen Elizabeth's husband is titled a prince.