After the shipwreck scene...

Elsa makes the decision that her journey must continue north to Athohellan. However, the journey must be made by her alone. Having Anna along with her is an unacceptable risk with the danger involved going there.

Hats off first to JLATS for an excellent review of the shipwreck when Elsa could not contain the raw emotion from seeing the ice image of how her parents died and their voices as the wave broke through and swept them away. And Anna handling Elsa's emotional state the best way she could.

Anna tells her that Elsa is a gift from the spirits because of their mother, Iduna, rescued Agnarr, who was an enemy, from the fighting started by the dam. Elsa then surmises that the answers were to be found in Ahtohallan. And that she must make the journey alone. Of course, Anna objects, saying that Elsa promised to do this together, that Elsa needs to stop doing things alone all the time and that she does not want to lose her. They embrace, Elsa echoes those sentiments. Starting with this:

Then this scene:

Elsa makes the ice canoe, then with ine kick/stomp, sets Olaf and Anna down the ice path. Then we see this:

The look on Elsa's face says it all. Elsa was not happy in doing what she did, yet she had to do this, making her point. This has been used in two other films before that I know. "Gunsmoke, The Last Apache." Matt Dillon's lady friend who had his daughter with him, just got him out of a crooked Sherriff's jail, only wanting to then go with him, and Matt tricking her into a cell and locking the door! "Grand Torino" Clint Eastwood's character, "Walt Kowalski," had to trick Thao Bang Lor (Bee Vang) into Walt's basement, only for Walt to close and lock the door on it because of what Walt was going to do with the local gang to eliminate that threat, and Thao wouldn't stand a chance, and Walt gave his life to get ghe gang arrested and imprisoned on murder.

When Anna objected to Elsa going alone, she did have a valid reason. Elsa, as an introvert, even at the beginning of the movie, showed that she was wanting to do this alone. We've read about how those of us who have introvert tendencies, want to carry the load alone. Elsa did not object to everyone coming this far. Now facing the journey to Ahtohallan was going to be very dangerous for Anna to come along. In other words, the danger was waaaaay beyond Anna's "paygrade." Now Elsa had a choice, keep the promise and put Anna in grave danger, or break it for now, for Anna's and Olaf's safety. Elsa chose the safety option. And as we know, they finally did together in the end!