As made evident up to this moment, the two things in the world Elsa fears the most are losing Anna, and herself. More specifically, the damage her powers could do as per prophesied by Pabbie in her youth.
Before Elsa turns around, you’ll notice how exhausted she is. Her fear took over and took its toll. Her eyes are full of regret, saying, “I can’t believe I just said that. These are my problems, and they should stay that way. I can’t believe I just made them Anna’s too.” The way she blinks right before she turns is a sign she’s building the courage to. Elsa exhales slowly, preparing herself to face the only person she’s ever spilled her heart out to. The trouble is, her heart kind of sort of literally spilled into Anna’s in not the most heartwarming way. Ironically, it was the most heartchilling way possible.
Turning around, Elsa was as ready as she’d ever be to face Anna. What she forgot to prepare herself for was facing both of her fears in the same host. Losing Anna because of her powers— the first step she took closer to her sister in thirteen years being the only thing to blame.
You’d think, loving your sister as much as Elsa does, the older would run to the younger’s side to comfort her. Heck, Kristoff and Anna met not a day ago and he does just that. It’s instinct, but Elsa flinches, gasps, backs away, and closes her hands. Fear takes over as she silently asks, “Anna, what happened?” She backs away slowly, giving herself the time to think. Until she realizes: “I happened.” Which is why she closes her hands and pulls them in towards her chest. She’s relapsing. She felt thirteen years of fear in thirty seconds. More importantly, she felt. So much for being a daddy’s girl.
Had she concealed it, Anna would have left the castle with no more than a bitterness towards her. Not slowly starting to die because Elsa let herself feel.
Yet, despite everything, Anna, not once, ever blames Elsa for anything. Perhaps, that’s what hurts the most. They literally love each other so much…it hurts.