Chelsea is the main character and does a majority of the talking in the pilot. For context, she is about half of all the dialogue, at somewhere between 700-750 words. I completely understand this is a large undertaking, and want anyone trying out just to be fully aware what they are signing up for. I will link the script if you want to skim through it and decide for yourself how you feel!

https://docs.google.com/document/d/1Y0IZn6o5OE-jBv7_wXaFWxkFff8q0sFso-UMynXZWl8/edit?tab=t.djs8m7wno5tu

For the pilot, Chelsea is 15 years old, but grows into adulthood within the first 3 episodes. I don't necessarily think her voice needs to change, assuming you were interested in this role long term, but figured I'd mention since some people may view that as an important detail.

Chelsea is smart, quick witted, and has a rather sharp tongue. A lot of sarcasm and dry humor. A great deal of her personality is putting on airs, wanting to seem cool, uncaring, and independent. In reality, Chelsea is emotional, desperate for approval, and horribly lonely. She often treats relationships as transactional, as that way they can remain "fair". 

Chelsea definitely sounds like she comes from money, and this often plays into her sarcasm or condescension. In the pilot, she is still a teen, and so is particularly bad at understanding her own feelings and regulating herself properly in that regard. "Petulant" is a good word to describe her.

Chelsea is a pretty dynamic character. Her status quo is definitely more flat or sarcastic, but often has big emotional bursts. Shouting, crying, and embarrassment can often crack through the uncaring facade.