I've been for a few hours.
In Frozen we see how Elsa plays the older sister’s role, she takes decisions, she sends Anna home, she tries to protect her from herself and she also tries to teach her how to skate. In OFA she apologizes to Anna, she almost feels maternal at some point, and in Frozen Fever despite being the one who was taken care of at the end, organizes Anna’s birthday showering her with love and attentions for a whole day. Everything from the first movie/short movies gave me a “big sister/good queen” vibe.
Then the Frozen 2 leaks arrived and everything turned upside down. Elsa’s feeling left out when she watches Anna and Kristoff (Annecy leaks), Elsa’s feeling out of place during the harvest festival (balcony scene) and then we see Anna holding her and helping her to fall asleep by doing what their mother did when they were kids (stroking her nose). It was kinda weird and I really wondered why Anna was suddently painted as the one who takes charge, helps the older sister to fall asleep, takes her in her arms like a baby, and all that shit. The vibe I got was that the dynamic was completely different.
I guess the feeling was right and from those little interactions they already wanted to push the viewer towards the new story: Elsa’s not happy there, Anna is the one who takes care of her so this HAS to mean she can take care of a whole kingdom. Too bad it really came out of nowhere.