In the Magic Kingdom head over to Adventureland next to the Flying Carpet ride you can meet both Princess Jasmine and Aladdin together.
At Epcot in the Morocco pavilion of World Showcase you can meet Jasmine inside the Lamps of Wonder.
Princess Jasmine could also appear at Cinderellas Royal Table in the Magic Kingdom or Akershus Royal Banquet Hall. The princess at these dining locations are not guaranteed so if you definitely want to see Jasmine her official meeting places. Neither of her greeting spots offer fastpass so make sure you pick up a times guide to see when she will available.