Growing up with the dumbest(But sweetest) fairies alive i think she'll forget.

Shes so busy

Probabably too busy with the restaurant. Man I was just wondering why you didn't include all of them and I was like ohhh.... yeah that's why.

She didn't grow up with someone she thought she was her mother, she just grew up with three fairies who she thought were her aunts. She probably doesn't even know the holiday even exists.

^ I think it means if all the Princesses were already informed about it since you can't forget something you've never been told about. ;)

I'd say Tiana or Mulan. I doubt Rapunzel would forget and I don't think Aurora would either for some reason.

what about the other princesses?

^ Well, I guess we only have those choices because other official Disney princesses don't have mothers or at least we don't know anything about them, they are either deseased or absent, like with Belle, Jasmine or Pocahontas.

Anyway, I think maybe Aurora forgets it because she didn't grow up with her parents and she just didn't get used to celebrating mother's day with her mom.

I think she wouldn't have listened about this day called "mother's day".

Aurora: She's probably never heard of Mother's day until she turned 16, so she wouldn't remember. And her mom is so nice she wouldn't be that mad.
Mulan: She would shame her family & ancestors if she forgot such an important holiday.
Tiana: She's already so responsible, I can't imagine her being careless.
Rapunzel: How could she forget when she's got nothing else to do? Also Mother Gother would be furious, and Rapunzel would remember that and remember for her real mom.

But out of all the princesses, definitely Ariel.

Or Mulan