Haru was a stubborn, lazy, somewhat ditzy, and awkward at the beginning of the movie. But by the end of the movie she is bold, mature, and confident. You can tell she changed a lot after the return from the Cat Kingdom.
Right at the beginning of the movie she came late at school that the teacher points out. Then the whole classes start laughing at her, even her crush Machida. She likes to goofing around with her best friend Hiromi. She is messy that you can see physically in her room:
She is wishy-washy about many things that cause misunderstanding with simple-hearted Natoru. So she got right into trouble. She get more confidence and resolve as the story progress. Yuki and the baron encourage her to do so.
Even she is clumsy humans and cats like her for her honestly and cooperatively attitude. Because of that attitude many cats become her allies and help her to escape the Cat Kingdom.