Why is Merida considered to be a disney Princess?

All of Pixar's feature length cine have been credited as Disney/Pixar collaborations. I'm not entirely sure how involved the employees of Walt disney Pictures are in Pixar's movies, but I had a feeling it was the work of más than one studio, and disney have been doing a bit más than just distributing. It might even just be that some of the individual employees go between the two studios, I've never been too sure. But I think disney does actually get involved in the production of Pixar's feature length movies.

I also expect she gets away with it because pixar had already been bought out por disney por the time the movie was created. I think Valiente was pitched around 2008? And disney bought pixar in 2006. I'm half expecting a Marvel o LucasFilm character to be added to their princess line-up someday. XD