King Agdar and Queen Idunn are about to leave for a sea voyage. Elsa is in her room again – still – in the middle of a snowstorm that mirrors the agitation inside, the fear at not having her parents there to do…what? Whatever they can do for her. Flakes swirl through the air, as the wind jostles loose items in her room.
Anna walks past, hesitates, almost stops to knock (for all the good it's ever done.)
She keeps on walking.
And in another world, only differing by the weight of a snowflake…
A glass on Elsa's desk is wobbling, overbalanced. A single flake of snow lands on it just so, just enough to tip it off the table, crashing to the floor. Anna hears the crash, pauses, listens.
She hears Elsa say "Dammit!" And then she hears sobbing. She hears Elsa pleading with gods she's lost faith in, begging them not to let her parents go, not yet, she isn't ready. Anna hears her sister, her soul in distress. She has to do something.
She goes to her parents, tells them what she heard. Begs them to stay, for Elsa's sake. Pleads as tearfully as Elsa would if she dared. Their hearts already full of misgivings, they relent. For Elsa, and for Anna, they stay.
Later, they discover to their horror (and secret relief) that the ship they would've taken sank with all hands. Idunn resolves that they'll never leave Elsa's side again.
As the years pass, Agdar finds it harder to hide his frustration with Elsa's lack of progress. And Elsa finds it harder to conceal the frustration she feels with him, with both of them, for the demands they make on her, for the help they can't provide. She doesn't need to internalize the responsibility the way she would if they weren't there nagging her every day, asking for progress that never comes, keeping their tight restrictions on a young girl becoming a young woman. They force her to learn to be queen – and she excels at it – even though they may have fifty years or more before ceding the throne to her. Her isolation – her life – stretches before her like an unending dirt road. No change, no hope, just isolation and resentment.
She lashes out with her magic. It feels good. It feels free. After years of having to keep it inside, she dares to unleash her magic deliberately. And it feels wonderful. She practices in secret, mastering her powers, hiding her joy the way she hid her fear.
Finally, she decides that she deserves to control her own life. That she deserves her birthright. She confronts her parents in a rage, making them cower. She sees the terror in their eyes, and imagines how they must see her. Not a princess or a daughter or a woman. A monster. A dangerous monster. She literally storms out. She marches up the North Mountain and builds a palace for herself. If they think she's a monster, she'll be the worst monster they can imagine.
She returns from the mountain leading an army of snowmen that bristle with icy spikes, carrying trees like clubs. There's a pitched battle against the army of Arendelle, closer fought than she expected since something is blocking her blasts of magic. She fights through until she confronts her parents again.
She discovers that the trolls have been helping them, blocking magic with magic. But it still wasn't enough to stop her. She threatens them with needle-sharp jags of ice…
Until Anna bursts in to see what's going on. Elsa sees Anna's amazement at her powers – and Anna's horror at what Elsa was about to do.
She gives them a day to prepare their surrender, then goes to confront the trolls.
Winter can split rock. It can certainly split rock trolls. After a brief confrontation between Elsa and Kristoff, frost accumulates threateningly on Bulda as Elsa demands that Grand Pabbie give her what she wants. No armies against her. No Agdar or Idunn between her and the throne. The devotion of her people.
Pabbie adheres to the letter of her demands. He sends her to another world. A world where her parents died at sea. A world where the people of Arendelle adore their queen. A world where Agdar and Idunn don't stand between her and the throne, but another Elsa does. A world that, in the end, only differed by the weight of a snowflake.