I'm not sure about plus sized, but when you post that picture with this title, it seems like you're suggesting the princess on the right side is "plus size". Not even close. If that woman existed in real life, she'd still be incredibly thin. The issue is that Disney animation frequently makes females characters impossibly and cartoonishly thin. The princess on the left would be dead. She certainly wouldn't be able to walk. Now, yes, it IS a cartoon, so body proportions should be taken with a grain of salt.. yet, the male characters are always more realistically proportioned. Their shoulders, waists, wrists tend to be much more realistic.
On one hand, I think a cartoon art style is a cartoon art style. But in a society where body image is literally the death of some girls, maybe Disney could do with making princesses at least realistically thin - especially with the noticeable contrast between the female and the male characters.
I have no personal issue with having a plus size princess, but I am interested in Disney making the princess on the right, more often than the princess on the left. More realistic proportions would be really cool.