I think what's so hard for me to make a list of which princesses are the most intelligent is that none of them really give consistent evidence that they're smart. All the princesses do something foolish, but I think sometimes too the people on this site aligns taking risks with stupidity. Someone can be extremely smart but if they're put in a tight spot where they need to do something risky to get what they want (Ariel, Rapunzel, Mulan, etc) they're often lauded as stupid.
That being said, we haven't been given a princess really whose intelligence is really played out. That's consistently clever, like Aladdin (who is another one I think is obviously clever but lacks common sense).

No, I don't think so.

Second smartest after Mulan

^^what? did you even read the question?