Keep Moving Forward
You're right, she walks totally different from the other princesses. They all kinda glide with their arms held in weird poses. Merida takes longer strides and swings her arms.If you watch the video, her mannerisms are totally different from the other, more traditional princesses. She just hops off her horse and strolls up to the castle very casually. So at least for now the actual character at the parks is Merida-esque.
I personally don't care about her new look because I couldn't stand that movie (couldn't even finish it) but I would hate for Merida to become a cookie cutter princess.