I think all of them were except for Pocahontas. I just can't see Pocahontas being bullied at all, maybe some found her odd but I don't think any of them would bully her. Tiana I think maybe she might have been bullied by racist white kids. With Belle we already knew people thought she was odd and maybe as a kid she was picked on and she just learned to deal with it. I'm positive Ariel was bullied, despite being a princess. We know for one she was bullied by her sisters in the TV series, especially Arista. I'm pretty sure everyone is aware of her love for human things and people bully her. Mulan, do I even need to explain why? I didn't include Snow White and Cinderella because they didn't have much contact with the world and were controlled by their step-families. Aurora, Jasmine, and Rapunzel were isolated.

I think all of them were at some point. Anyone could get bullied for the most ridiculous thing. But I picked Mulan for obvious reasons like you said.

or Mulan

And Tiana. Alll of them, to some extent. Good question!

I think Belle and Tiana both were in their movies, and Mulan to an extent. I don't know if what Ariel's father did would really constitute as bullying, and Pocahontas sort of was by Ratcliffe, and she definitely was in the sequel. I just think Tiana was/ would have been to the greatest extent, considering the racial climate of the South in the twenties.

I think people treat Belle just differently but they wouldn't bully her because she's kind and pretty and she hasn't done anything to anyone(or maybe Gaston during the movie).
Tiana was probably very bullied but she did have friends who tried to get her around with them though she has always too much work. I just can't see Ariel or Pocahontas be bullied at least not much, I don't think anyone would have dared.
I chose Mulan because she didn't seem to have other friends than her dog and horse before she went army. Fact that she didn't have friends put her above Tiana in my list. And Mulan had to care what people thinks about her and because it's more likely that others really bullied her I chose her above Belle.

I thought belle would have been because of how 'different' she was compared to the other french girls

or Tiana or Belle. I don't think Ariel and Poca were bullied.