Jasmine is actually very kind to those who deserve it.

Jasmine is not kind, the merchant deserved to be paid for what she stole, yet since she's a priviliged princess she can do whatever she wants. She's never shown any interest on anyone but herself.

All the other princesses who are kind is blatantly stated, like Cinderella, Rapunzel, Snowwhite, etc. while Mulan gives back the toy to the girl at the beginning and is shown as having a good heart but everyone speaks about her bravery and not her kindness