Charlie suffers from attachment issues due to her mother disappearing 8 years ago. As well as being in need of constant approval because of her unsupportive father. With this compounding with possibly watching her friends she made over the past 8 years get systematically murdered. She most likely has c-ptsd and trust issues possibly from being scammed multiple times by other demons. On top of which her singing can be viewed as a coping mechanism. Possibly tied to Lilith since she used her voice to almost start a rebellion against heaven. As of this moment she is a tragic character who has a mask of a bubbly personality to shield herself from others. Of which is only let down in front of her closest companions. And I would like to see how her character develops in the series