She can't hide from Elsa, not when she comes home late, all dressed up. Elsa smiles and asks about her day, tries to resume some normalcy, and the words tumble out before Anna can bite them back.
"I had a date," she says, voice as desperate as the words. She'd kissed Elsa only last week! This isn't 'moving on', this is rebound. She knows it, Elsa knows it.
But Elsa doesn't call her out on it, for which Anna is grateful.
She can't be any weaker in front of Elsa than she's already been.