Both Elsa and Anna had flawed reasoning in this scene. Elsa's solution to her problems always appears to be running away, or walking out and ending the party in this case - facing them head-on never seems to occur to her in the film, which is understandable considering the mind-set she's been forced to frame since childhood ("Conceal, don't feel"). But she needs to learn to lean on other people in order to overcome her fears, when isolation only makes things worse.
Anna is justified in asking Elsa outright for an explanation of her behaviour, since Elsa's nature won't allow a voluntary disclosure. The problem was her approach; instead of taking her sister aside, she yelled at her when she was already upset, in the middle of a large crowd - a course of action which could only cause further anxiety for Elsa - in an outpouring of anger and hurt. These emotions are totally understandable. But Anna's selfish preoccupation with her own problems blinded her to those of her sister. Ultimately, both Anna and Elsa are human and flawed.

I LOVED HOW YOU SAID THAT!!!!!! you are so right, i put elsa, but only because i like her better. lol! they are both human and have many flaws