The Disney princess lineup has always had some odd inclusions and exclusions. Mulan is considered a Disney princess^TM despite not actually having the title, as is Alice (some random girl), Pocahontas (chieftain's daughter, which I guess you can argue is a similar concept), Moana (see above), Mirabel (another random girl without a position of authority), Tinker Bell, Jane Porter (although she is a noble, which is at least similar) and Megara. (From Hercules, in case you also forget that movie existed)
Likewise, the lineup does not include Nala, despite actually possessing the title explicitly. (Is Disney racist against lions or something?) Nor does it include Eilonwy, though that's understandable considering The Black Cauldron flopped so hard it nearly tanked their animation department. It doesn't include any acquired properties either, so as funny as it is to lump Leia into the group, officially she doesn't count.
Alice, Mirabel, Tinkerbell, Jane, and Megara aren't Disney Princesses. You can find an exhaustive list at https://princess.disney.com/. Not all Disney movies have princesses, but all princesses have movies and must be actual royals in the movie by the end (according to local culture). They must also be humans.
I included ones that were considered a part of the lineup in the past, but were later discontinued. The princess lineup is flexible and liable to change at any given time. Most of the characters I've listed were promoted as princesses for at least a little while following the release of their respective movies. Alice was promoted as an initial member of the line when it was first conceived and her status as one is a plot point in Kingdom Hearts, and Tinker Bell was a part of the line prior to the existence of the Disney Fairies line. The official website only lists the current lineup, not it's entire history.