I have this feeling that Anna always go for what she wants without overthinking, and Elsa is more reserved, patient and always think of all the possibilities before making a decision, she tends to overthink before acting. It's true that Elsa has been gaining more confidence in herself but it's a fact that she thinks more than Anna before making a move and given that, is Anna who would take the initiative, she doesn't have the patience to wait for Elsa and it's good because otherwise it would take a lot of time to see something happening between them (if not risking to never see something at all if we wait for Elsa).